diff --git a/changelog.d/13273.feature b/changelog.d/13273.feature
new file mode 100644
index 0000000000..53110d74e9
--- /dev/null
+++ b/changelog.d/13273.feature
@@ -0,0 +1 @@
+Add support for stable prefixes for [MSC2285 (private read receipts)](https://github.com/matrix-org/matrix-spec-proposals/pull/2285).
diff --git a/synapse/api/constants.py b/synapse/api/constants.py
index 789859e69e..1d46fb0e43 100644
--- a/synapse/api/constants.py
+++ b/synapse/api/constants.py
@@ -257,7 +257,8 @@ class GuestAccess:
 
 class ReceiptTypes:
     READ: Final = "m.read"
-    READ_PRIVATE: Final = "org.matrix.msc2285.read.private"
+    READ_PRIVATE: Final = "m.read.private"
+    UNSTABLE_READ_PRIVATE: Final = "org.matrix.msc2285.read.private"
     FULLY_READ: Final = "m.fully_read"
 
 
diff --git a/synapse/config/experimental.py b/synapse/config/experimental.py
index c2ecd977cd..7d17c958bb 100644
--- a/synapse/config/experimental.py
+++ b/synapse/config/experimental.py
@@ -32,7 +32,7 @@ class ExperimentalConfig(Config):
         # MSC2716 (importing historical messages)
         self.msc2716_enabled: bool = experimental.get("msc2716_enabled", False)
 
-        # MSC2285 (private read receipts)
+        # MSC2285 (unstable private read receipts)
         self.msc2285_enabled: bool = experimental.get("msc2285_enabled", False)
 
         # MSC3244 (room version capabilities)
diff --git a/synapse/handlers/initial_sync.py b/synapse/handlers/initial_sync.py
index 85b472f250..6484e47e5f 100644
--- a/synapse/handlers/initial_sync.py
+++ b/synapse/handlers/initial_sync.py
@@ -143,8 +143,8 @@ class InitialSyncHandler:
             joined_rooms,
             to_key=int(now_token.receipt_key),
         )
-        if self.hs.config.experimental.msc2285_enabled:
-            receipt = ReceiptEventSource.filter_out_private_receipts(receipt, user_id)
+
+        receipt = ReceiptEventSource.filter_out_private_receipts(receipt, user_id)
 
         tags_by_room = await self.store.get_tags_for_user(user_id)
 
@@ -456,11 +456,8 @@ class InitialSyncHandler:
             )
             if not receipts:
                 return []
-            if self.hs.config.experimental.msc2285_enabled:
-                receipts = ReceiptEventSource.filter_out_private_receipts(
-                    receipts, user_id
-                )
-            return receipts
+
+            return ReceiptEventSource.filter_out_private_receipts(receipts, user_id)
 
         presence, receipts, (messages, token) = await make_deferred_yieldable(
             gather_results(
diff --git a/synapse/handlers/receipts.py b/synapse/handlers/receipts.py
index 43d2882b0a..d4a866b346 100644
--- a/synapse/handlers/receipts.py
+++ b/synapse/handlers/receipts.py
@@ -163,7 +163,10 @@ class ReceiptsHandler:
         if not is_new:
             return
 
-        if self.federation_sender and receipt_type != ReceiptTypes.READ_PRIVATE:
+        if self.federation_sender and receipt_type not in (
+            ReceiptTypes.READ_PRIVATE,
+            ReceiptTypes.UNSTABLE_READ_PRIVATE,
+        ):
             await self.federation_sender.send_read_receipt(receipt)
 
 
@@ -203,24 +206,38 @@ class ReceiptEventSource(EventSource[int, JsonDict]):
             for event_id, orig_event_content in room.get("content", {}).items():
                 event_content = orig_event_content
                 # If there are private read receipts, additional logic is necessary.
-                if ReceiptTypes.READ_PRIVATE in event_content:
+                if (
+                    ReceiptTypes.READ_PRIVATE in event_content
+                    or ReceiptTypes.UNSTABLE_READ_PRIVATE in event_content
+                ):
                     # Make a copy without private read receipts to avoid leaking
                     # other user's private read receipts..
                     event_content = {
                         receipt_type: receipt_value
                         for receipt_type, receipt_value in event_content.items()
-                        if receipt_type != ReceiptTypes.READ_PRIVATE
+                        if receipt_type
+                        not in (
+                            ReceiptTypes.READ_PRIVATE,
+                            ReceiptTypes.UNSTABLE_READ_PRIVATE,
+                        )
                     }
 
                     # Copy the current user's private read receipt from the
                     # original content, if it exists.
-                    user_private_read_receipt = orig_event_content[
-                        ReceiptTypes.READ_PRIVATE
-                    ].get(user_id, None)
+                    user_private_read_receipt = orig_event_content.get(
+                        ReceiptTypes.READ_PRIVATE, {}
+                    ).get(user_id, None)
                     if user_private_read_receipt:
                         event_content[ReceiptTypes.READ_PRIVATE] = {
                             user_id: user_private_read_receipt
                         }
+                    user_unstable_private_read_receipt = orig_event_content.get(
+                        ReceiptTypes.UNSTABLE_READ_PRIVATE, {}
+                    ).get(user_id, None)
+                    if user_unstable_private_read_receipt:
+                        event_content[ReceiptTypes.UNSTABLE_READ_PRIVATE] = {
+                            user_id: user_unstable_private_read_receipt
+                        }
 
                 # Include the event if there is at least one non-private read
                 # receipt or the current user has a private read receipt.
@@ -256,10 +273,9 @@ class ReceiptEventSource(EventSource[int, JsonDict]):
             room_ids, from_key=from_key, to_key=to_key
         )
 
-        if self.config.experimental.msc2285_enabled:
-            events = ReceiptEventSource.filter_out_private_receipts(
-                events, user.to_string()
-            )
+        events = ReceiptEventSource.filter_out_private_receipts(
+            events, user.to_string()
+        )
 
         return events, to_key
 
diff --git a/synapse/replication/tcp/client.py b/synapse/replication/tcp/client.py
index e4f2201c92..1ed7230e32 100644
--- a/synapse/replication/tcp/client.py
+++ b/synapse/replication/tcp/client.py
@@ -416,7 +416,10 @@ class FederationSenderHandler:
             if not self._is_mine_id(receipt.user_id):
                 continue
             # Private read receipts never get sent over federation.
-            if receipt.receipt_type == ReceiptTypes.READ_PRIVATE:
+            if receipt.receipt_type in (
+                ReceiptTypes.READ_PRIVATE,
+                ReceiptTypes.UNSTABLE_READ_PRIVATE,
+            ):
                 continue
             receipt_info = ReadReceipt(
                 receipt.room_id,
diff --git a/synapse/rest/client/notifications.py b/synapse/rest/client/notifications.py
index 24bc7c9095..a73322a6a4 100644
--- a/synapse/rest/client/notifications.py
+++ b/synapse/rest/client/notifications.py
@@ -58,7 +58,12 @@ class NotificationsServlet(RestServlet):
         )
 
         receipts_by_room = await self.store.get_receipts_for_user_with_orderings(
-            user_id, [ReceiptTypes.READ, ReceiptTypes.READ_PRIVATE]
+            user_id,
+            [
+                ReceiptTypes.READ,
+                ReceiptTypes.READ_PRIVATE,
+                ReceiptTypes.UNSTABLE_READ_PRIVATE,
+            ],
         )
 
         notif_event_ids = [pa.event_id for pa in push_actions]
diff --git a/synapse/rest/client/read_marker.py b/synapse/rest/client/read_marker.py
index 8896f2df50..aaad8b233f 100644
--- a/synapse/rest/client/read_marker.py
+++ b/synapse/rest/client/read_marker.py
@@ -40,9 +40,13 @@ class ReadMarkerRestServlet(RestServlet):
         self.read_marker_handler = hs.get_read_marker_handler()
         self.presence_handler = hs.get_presence_handler()
 
-        self._known_receipt_types = {ReceiptTypes.READ, ReceiptTypes.FULLY_READ}
+        self._known_receipt_types = {
+            ReceiptTypes.READ,
+            ReceiptTypes.FULLY_READ,
+            ReceiptTypes.READ_PRIVATE,
+        }
         if hs.config.experimental.msc2285_enabled:
-            self._known_receipt_types.add(ReceiptTypes.READ_PRIVATE)
+            self._known_receipt_types.add(ReceiptTypes.UNSTABLE_READ_PRIVATE)
 
     async def on_POST(
         self, request: SynapseRequest, room_id: str
diff --git a/synapse/rest/client/receipts.py b/synapse/rest/client/receipts.py
index 409bfd43c1..c6108fc5eb 100644
--- a/synapse/rest/client/receipts.py
+++ b/synapse/rest/client/receipts.py
@@ -44,11 +44,13 @@ class ReceiptRestServlet(RestServlet):
         self.read_marker_handler = hs.get_read_marker_handler()
         self.presence_handler = hs.get_presence_handler()
 
-        self._known_receipt_types = {ReceiptTypes.READ}
+        self._known_receipt_types = {
+            ReceiptTypes.READ,
+            ReceiptTypes.READ_PRIVATE,
+            ReceiptTypes.FULLY_READ,
+        }
         if hs.config.experimental.msc2285_enabled:
-            self._known_receipt_types.update(
-                (ReceiptTypes.READ_PRIVATE, ReceiptTypes.FULLY_READ)
-            )
+            self._known_receipt_types.add(ReceiptTypes.UNSTABLE_READ_PRIVATE)
 
     async def on_POST(
         self, request: SynapseRequest, room_id: str, receipt_type: str, event_id: str
diff --git a/synapse/rest/client/versions.py b/synapse/rest/client/versions.py
index 0366986755..c9a830cbac 100644
--- a/synapse/rest/client/versions.py
+++ b/synapse/rest/client/versions.py
@@ -94,6 +94,7 @@ class VersionsRestServlet(RestServlet):
                     # Supports the busy presence state described in MSC3026.
                     "org.matrix.msc3026.busy_presence": self.config.experimental.msc3026_enabled,
                     # Supports receiving private read receipts as per MSC2285
+                    "org.matrix.msc2285.stable": True,  # TODO: Remove when MSC2285 becomes a part of the spec
                     "org.matrix.msc2285": self.config.experimental.msc2285_enabled,
                     # Supports filtering of /publicRooms by room type as per MSC3827
                     "org.matrix.msc3827.stable": True,
diff --git a/synapse/storage/databases/main/event_push_actions.py b/synapse/storage/databases/main/event_push_actions.py
index 5db70f9a60..161aad0f89 100644
--- a/synapse/storage/databases/main/event_push_actions.py
+++ b/synapse/storage/databases/main/event_push_actions.py
@@ -80,7 +80,7 @@ import attr
 
 from synapse.api.constants import ReceiptTypes
 from synapse.metrics.background_process_metrics import wrap_as_background_process
-from synapse.storage._base import SQLBaseStore, db_to_json
+from synapse.storage._base import SQLBaseStore, db_to_json, make_in_list_sql_clause
 from synapse.storage.database import (
     DatabasePool,
     LoggingDatabaseConnection,
@@ -259,7 +259,11 @@ class EventPushActionsWorkerStore(ReceiptsWorkerStore, StreamWorkerStore, SQLBas
             txn,
             user_id,
             room_id,
-            receipt_types=(ReceiptTypes.READ, ReceiptTypes.READ_PRIVATE),
+            receipt_types=(
+                ReceiptTypes.READ,
+                ReceiptTypes.READ_PRIVATE,
+                ReceiptTypes.UNSTABLE_READ_PRIVATE,
+            ),
         )
 
         stream_ordering = None
@@ -448,6 +452,7 @@ class EventPushActionsWorkerStore(ReceiptsWorkerStore, StreamWorkerStore, SQLBas
             The list will be ordered by ascending stream_ordering.
             The list will have between 0~limit entries.
         """
+
         # find rooms that have a read receipt in them and return the next
         # push actions
         def get_after_receipt(
@@ -455,7 +460,18 @@ class EventPushActionsWorkerStore(ReceiptsWorkerStore, StreamWorkerStore, SQLBas
         ) -> List[Tuple[str, str, int, str, bool]]:
             # find rooms that have a read receipt in them and return the next
             # push actions
-            sql = """
+
+            receipt_types_clause, args = make_in_list_sql_clause(
+                self.database_engine,
+                "receipt_type",
+                (
+                    ReceiptTypes.READ,
+                    ReceiptTypes.READ_PRIVATE,
+                    ReceiptTypes.UNSTABLE_READ_PRIVATE,
+                ),
+            )
+
+            sql = f"""
                 SELECT ep.event_id, ep.room_id, ep.stream_ordering, ep.actions,
                     ep.highlight
                 FROM (
@@ -463,10 +479,10 @@ class EventPushActionsWorkerStore(ReceiptsWorkerStore, StreamWorkerStore, SQLBas
                         MAX(stream_ordering) as stream_ordering
                     FROM events
                     INNER JOIN receipts_linearized USING (room_id, event_id)
-                    WHERE receipt_type = 'm.read' AND user_id = ?
+                    WHERE {receipt_types_clause} AND user_id = ?
                     GROUP BY room_id
                 ) AS rl,
-                    event_push_actions AS ep
+                event_push_actions AS ep
                 WHERE
                     ep.room_id = rl.room_id
                     AND ep.stream_ordering > rl.stream_ordering
@@ -476,7 +492,9 @@ class EventPushActionsWorkerStore(ReceiptsWorkerStore, StreamWorkerStore, SQLBas
                     AND ep.notif = 1
                 ORDER BY ep.stream_ordering ASC LIMIT ?
             """
-            args = [user_id, user_id, min_stream_ordering, max_stream_ordering, limit]
+            args.extend(
+                (user_id, user_id, min_stream_ordering, max_stream_ordering, limit)
+            )
             txn.execute(sql, args)
             return cast(List[Tuple[str, str, int, str, bool]], txn.fetchall())
 
@@ -490,7 +508,17 @@ class EventPushActionsWorkerStore(ReceiptsWorkerStore, StreamWorkerStore, SQLBas
         def get_no_receipt(
             txn: LoggingTransaction,
         ) -> List[Tuple[str, str, int, str, bool]]:
-            sql = """
+            receipt_types_clause, args = make_in_list_sql_clause(
+                self.database_engine,
+                "receipt_type",
+                (
+                    ReceiptTypes.READ,
+                    ReceiptTypes.READ_PRIVATE,
+                    ReceiptTypes.UNSTABLE_READ_PRIVATE,
+                ),
+            )
+
+            sql = f"""
                 SELECT ep.event_id, ep.room_id, ep.stream_ordering, ep.actions,
                     ep.highlight
                 FROM event_push_actions AS ep
@@ -498,7 +526,7 @@ class EventPushActionsWorkerStore(ReceiptsWorkerStore, StreamWorkerStore, SQLBas
                 WHERE
                     ep.room_id NOT IN (
                         SELECT room_id FROM receipts_linearized
-                        WHERE receipt_type = 'm.read' AND user_id = ?
+                        WHERE {receipt_types_clause} AND user_id = ?
                         GROUP BY room_id
                     )
                     AND ep.user_id = ?
@@ -507,7 +535,9 @@ class EventPushActionsWorkerStore(ReceiptsWorkerStore, StreamWorkerStore, SQLBas
                     AND ep.notif = 1
                 ORDER BY ep.stream_ordering ASC LIMIT ?
             """
-            args = [user_id, user_id, min_stream_ordering, max_stream_ordering, limit]
+            args.extend(
+                (user_id, user_id, min_stream_ordering, max_stream_ordering, limit)
+            )
             txn.execute(sql, args)
             return cast(List[Tuple[str, str, int, str, bool]], txn.fetchall())
 
@@ -557,12 +587,23 @@ class EventPushActionsWorkerStore(ReceiptsWorkerStore, StreamWorkerStore, SQLBas
             The list will be ordered by descending received_ts.
             The list will have between 0~limit entries.
         """
+
         # find rooms that have a read receipt in them and return the most recent
         # push actions
         def get_after_receipt(
             txn: LoggingTransaction,
         ) -> List[Tuple[str, str, int, str, bool, int]]:
-            sql = """
+            receipt_types_clause, args = make_in_list_sql_clause(
+                self.database_engine,
+                "receipt_type",
+                (
+                    ReceiptTypes.READ,
+                    ReceiptTypes.READ_PRIVATE,
+                    ReceiptTypes.UNSTABLE_READ_PRIVATE,
+                ),
+            )
+
+            sql = f"""
                 SELECT ep.event_id, ep.room_id, ep.stream_ordering, ep.actions,
                     ep.highlight, e.received_ts
                 FROM (
@@ -570,7 +611,7 @@ class EventPushActionsWorkerStore(ReceiptsWorkerStore, StreamWorkerStore, SQLBas
                         MAX(stream_ordering) as stream_ordering
                     FROM events
                     INNER JOIN receipts_linearized USING (room_id, event_id)
-                    WHERE receipt_type = 'm.read' AND user_id = ?
+                    WHERE {receipt_types_clause} AND user_id = ?
                     GROUP BY room_id
                 ) AS rl,
                 event_push_actions AS ep
@@ -584,7 +625,9 @@ class EventPushActionsWorkerStore(ReceiptsWorkerStore, StreamWorkerStore, SQLBas
                     AND ep.notif = 1
                 ORDER BY ep.stream_ordering DESC LIMIT ?
             """
-            args = [user_id, user_id, min_stream_ordering, max_stream_ordering, limit]
+            args.extend(
+                (user_id, user_id, min_stream_ordering, max_stream_ordering, limit)
+            )
             txn.execute(sql, args)
             return cast(List[Tuple[str, str, int, str, bool, int]], txn.fetchall())
 
@@ -598,7 +641,17 @@ class EventPushActionsWorkerStore(ReceiptsWorkerStore, StreamWorkerStore, SQLBas
         def get_no_receipt(
             txn: LoggingTransaction,
         ) -> List[Tuple[str, str, int, str, bool, int]]:
-            sql = """
+            receipt_types_clause, args = make_in_list_sql_clause(
+                self.database_engine,
+                "receipt_type",
+                (
+                    ReceiptTypes.READ,
+                    ReceiptTypes.READ_PRIVATE,
+                    ReceiptTypes.UNSTABLE_READ_PRIVATE,
+                ),
+            )
+
+            sql = f"""
                 SELECT ep.event_id, ep.room_id, ep.stream_ordering, ep.actions,
                     ep.highlight, e.received_ts
                 FROM event_push_actions AS ep
@@ -606,7 +659,7 @@ class EventPushActionsWorkerStore(ReceiptsWorkerStore, StreamWorkerStore, SQLBas
                 WHERE
                     ep.room_id NOT IN (
                         SELECT room_id FROM receipts_linearized
-                        WHERE receipt_type = 'm.read' AND user_id = ?
+                        WHERE {receipt_types_clause} AND user_id = ?
                         GROUP BY room_id
                     )
                     AND ep.user_id = ?
@@ -615,7 +668,9 @@ class EventPushActionsWorkerStore(ReceiptsWorkerStore, StreamWorkerStore, SQLBas
                     AND ep.notif = 1
                 ORDER BY ep.stream_ordering DESC LIMIT ?
             """
-            args = [user_id, user_id, min_stream_ordering, max_stream_ordering, limit]
+            args.extend(
+                (user_id, user_id, min_stream_ordering, max_stream_ordering, limit)
+            )
             txn.execute(sql, args)
             return cast(List[Tuple[str, str, int, str, bool, int]], txn.fetchall())
 
diff --git a/tests/handlers/test_receipts.py b/tests/handlers/test_receipts.py
index a95868b5c0..5f70a2db79 100644
--- a/tests/handlers/test_receipts.py
+++ b/tests/handlers/test_receipts.py
@@ -15,6 +15,8 @@
 from copy import deepcopy
 from typing import List
 
+from parameterized import parameterized
+
 from synapse.api.constants import EduTypes, ReceiptTypes
 from synapse.types import JsonDict
 
@@ -25,13 +27,16 @@ class ReceiptsTestCase(unittest.HomeserverTestCase):
     def prepare(self, reactor, clock, hs):
         self.event_source = hs.get_event_sources().sources.receipt
 
-    def test_filters_out_private_receipt(self):
+    @parameterized.expand(
+        [ReceiptTypes.READ_PRIVATE, ReceiptTypes.UNSTABLE_READ_PRIVATE]
+    )
+    def test_filters_out_private_receipt(self, receipt_type: str) -> None:
         self._test_filters_private(
             [
                 {
                     "content": {
                         "$1435641916114394fHBLK:matrix.org": {
-                            ReceiptTypes.READ_PRIVATE: {
+                            receipt_type: {
                                 "@rikj:jki.re": {
                                     "ts": 1436451550453,
                                 }
@@ -45,13 +50,18 @@ class ReceiptsTestCase(unittest.HomeserverTestCase):
             [],
         )
 
-    def test_filters_out_private_receipt_and_ignores_rest(self):
+    @parameterized.expand(
+        [ReceiptTypes.READ_PRIVATE, ReceiptTypes.UNSTABLE_READ_PRIVATE]
+    )
+    def test_filters_out_private_receipt_and_ignores_rest(
+        self, receipt_type: str
+    ) -> None:
         self._test_filters_private(
             [
                 {
                     "content": {
                         "$1dgdgrd5641916114394fHBLK:matrix.org": {
-                            ReceiptTypes.READ_PRIVATE: {
+                            receipt_type: {
                                 "@rikj:jki.re": {
                                     "ts": 1436451550453,
                                 },
@@ -84,13 +94,18 @@ class ReceiptsTestCase(unittest.HomeserverTestCase):
             ],
         )
 
-    def test_filters_out_event_with_only_private_receipts_and_ignores_the_rest(self):
+    @parameterized.expand(
+        [ReceiptTypes.READ_PRIVATE, ReceiptTypes.UNSTABLE_READ_PRIVATE]
+    )
+    def test_filters_out_event_with_only_private_receipts_and_ignores_the_rest(
+        self, receipt_type: str
+    ) -> None:
         self._test_filters_private(
             [
                 {
                     "content": {
                         "$14356419edgd14394fHBLK:matrix.org": {
-                            ReceiptTypes.READ_PRIVATE: {
+                            receipt_type: {
                                 "@rikj:jki.re": {
                                     "ts": 1436451550453,
                                 },
@@ -125,7 +140,7 @@ class ReceiptsTestCase(unittest.HomeserverTestCase):
             ],
         )
 
-    def test_handles_empty_event(self):
+    def test_handles_empty_event(self) -> None:
         self._test_filters_private(
             [
                 {
@@ -160,13 +175,18 @@ class ReceiptsTestCase(unittest.HomeserverTestCase):
             ],
         )
 
-    def test_filters_out_receipt_event_with_only_private_receipt_and_ignores_rest(self):
+    @parameterized.expand(
+        [ReceiptTypes.READ_PRIVATE, ReceiptTypes.UNSTABLE_READ_PRIVATE]
+    )
+    def test_filters_out_receipt_event_with_only_private_receipt_and_ignores_rest(
+        self, receipt_type: str
+    ) -> None:
         self._test_filters_private(
             [
                 {
                     "content": {
                         "$14356419edgd14394fHBLK:matrix.org": {
-                            ReceiptTypes.READ_PRIVATE: {
+                            receipt_type: {
                                 "@rikj:jki.re": {
                                     "ts": 1436451550453,
                                 },
@@ -207,7 +227,7 @@ class ReceiptsTestCase(unittest.HomeserverTestCase):
             ],
         )
 
-    def test_handles_string_data(self):
+    def test_handles_string_data(self) -> None:
         """
         Tests that an invalid shape for read-receipts is handled.
         Context: https://github.com/matrix-org/synapse/issues/10603
@@ -242,13 +262,16 @@ class ReceiptsTestCase(unittest.HomeserverTestCase):
             ],
         )
 
-    def test_leaves_our_private_and_their_public(self):
+    @parameterized.expand(
+        [ReceiptTypes.READ_PRIVATE, ReceiptTypes.UNSTABLE_READ_PRIVATE]
+    )
+    def test_leaves_our_private_and_their_public(self, receipt_type: str) -> None:
         self._test_filters_private(
             [
                 {
                     "content": {
                         "$1dgdgrd5641916114394fHBLK:matrix.org": {
-                            ReceiptTypes.READ_PRIVATE: {
+                            receipt_type: {
                                 "@me:server.org": {
                                     "ts": 1436451550453,
                                 },
@@ -273,7 +296,7 @@ class ReceiptsTestCase(unittest.HomeserverTestCase):
                 {
                     "content": {
                         "$1dgdgrd5641916114394fHBLK:matrix.org": {
-                            ReceiptTypes.READ_PRIVATE: {
+                            receipt_type: {
                                 "@me:server.org": {
                                     "ts": 1436451550453,
                                 },
@@ -296,13 +319,16 @@ class ReceiptsTestCase(unittest.HomeserverTestCase):
             ],
         )
 
-    def test_we_do_not_mutate(self):
+    @parameterized.expand(
+        [ReceiptTypes.READ_PRIVATE, ReceiptTypes.UNSTABLE_READ_PRIVATE]
+    )
+    def test_we_do_not_mutate(self, receipt_type: str) -> None:
         """Ensure the input values are not modified."""
         events = [
             {
                 "content": {
                     "$1435641916114394fHBLK:matrix.org": {
-                        ReceiptTypes.READ_PRIVATE: {
+                        receipt_type: {
                             "@rikj:jki.re": {
                                 "ts": 1436451550453,
                             }
@@ -320,7 +346,7 @@ class ReceiptsTestCase(unittest.HomeserverTestCase):
 
     def _test_filters_private(
         self, events: List[JsonDict], expected_output: List[JsonDict]
-    ):
+    ) -> None:
         """Tests that the _filter_out_private returns the expected output"""
         filtered_events = self.event_source.filter_out_private_receipts(
             events, "@me:server.org"
diff --git a/tests/rest/client/test_sync.py b/tests/rest/client/test_sync.py
index ae16184828..de0dec8539 100644
--- a/tests/rest/client/test_sync.py
+++ b/tests/rest/client/test_sync.py
@@ -38,7 +38,6 @@ from tests.federation.transport.test_knocking import (
     KnockingStrippedStateEventHelperMixin,
 )
 from tests.server import TimedOutException
-from tests.unittest import override_config
 
 
 class FilterTestCase(unittest.HomeserverTestCase):
@@ -390,6 +389,12 @@ class ReadReceiptsTestCase(unittest.HomeserverTestCase):
         sync.register_servlets,
     ]
 
+    def make_homeserver(self, reactor: MemoryReactor, clock: Clock) -> HomeServer:
+        config = self.default_config()
+        config["experimental_features"] = {"msc2285_enabled": True}
+
+        return self.setup_test_homeserver(config=config)
+
     def prepare(self, reactor: MemoryReactor, clock: Clock, hs: HomeServer) -> None:
         self.url = "/sync?since=%s"
         self.next_batch = "s0"
@@ -408,15 +413,17 @@ class ReadReceiptsTestCase(unittest.HomeserverTestCase):
         # Join the second user
         self.helper.join(room=self.room_id, user=self.user2, tok=self.tok2)
 
-    @override_config({"experimental_features": {"msc2285_enabled": True}})
-    def test_private_read_receipts(self) -> None:
+    @parameterized.expand(
+        [ReceiptTypes.READ_PRIVATE, ReceiptTypes.UNSTABLE_READ_PRIVATE]
+    )
+    def test_private_read_receipts(self, receipt_type: str) -> None:
         # Send a message as the first user
         res = self.helper.send(self.room_id, body="hello", tok=self.tok)
 
         # Send a private read receipt to tell the server the first user's message was read
         channel = self.make_request(
             "POST",
-            f"/rooms/{self.room_id}/receipt/org.matrix.msc2285.read.private/{res['event_id']}",
+            f"/rooms/{self.room_id}/receipt/{receipt_type}/{res['event_id']}",
             {},
             access_token=self.tok2,
         )
@@ -425,8 +432,10 @@ class ReadReceiptsTestCase(unittest.HomeserverTestCase):
         # Test that the first user can't see the other user's private read receipt
         self.assertIsNone(self._get_read_receipt())
 
-    @override_config({"experimental_features": {"msc2285_enabled": True}})
-    def test_public_receipt_can_override_private(self) -> None:
+    @parameterized.expand(
+        [ReceiptTypes.READ_PRIVATE, ReceiptTypes.UNSTABLE_READ_PRIVATE]
+    )
+    def test_public_receipt_can_override_private(self, receipt_type: str) -> None:
         """
         Sending a public read receipt to the same event which has a private read
         receipt should cause that receipt to become public.
@@ -437,7 +446,7 @@ class ReadReceiptsTestCase(unittest.HomeserverTestCase):
         # Send a private read receipt
         channel = self.make_request(
             "POST",
-            f"/rooms/{self.room_id}/receipt/{ReceiptTypes.READ_PRIVATE}/{res['event_id']}",
+            f"/rooms/{self.room_id}/receipt/{receipt_type}/{res['event_id']}",
             {},
             access_token=self.tok2,
         )
@@ -456,8 +465,10 @@ class ReadReceiptsTestCase(unittest.HomeserverTestCase):
         # Test that we did override the private read receipt
         self.assertNotEqual(self._get_read_receipt(), None)
 
-    @override_config({"experimental_features": {"msc2285_enabled": True}})
-    def test_private_receipt_cannot_override_public(self) -> None:
+    @parameterized.expand(
+        [ReceiptTypes.READ_PRIVATE, ReceiptTypes.UNSTABLE_READ_PRIVATE]
+    )
+    def test_private_receipt_cannot_override_public(self, receipt_type: str) -> None:
         """
         Sending a private read receipt to the same event which has a public read
         receipt should cause no change.
@@ -478,7 +489,7 @@ class ReadReceiptsTestCase(unittest.HomeserverTestCase):
         # Send a private read receipt
         channel = self.make_request(
             "POST",
-            f"/rooms/{self.room_id}/receipt/{ReceiptTypes.READ_PRIVATE}/{res['event_id']}",
+            f"/rooms/{self.room_id}/receipt/{receipt_type}/{res['event_id']}",
             {},
             access_token=self.tok2,
         )
@@ -590,7 +601,10 @@ class UnreadMessagesTestCase(unittest.HomeserverTestCase):
             tok=self.tok,
         )
 
-    def test_unread_counts(self) -> None:
+    @parameterized.expand(
+        [ReceiptTypes.READ_PRIVATE, ReceiptTypes.UNSTABLE_READ_PRIVATE]
+    )
+    def test_unread_counts(self, receipt_type: str) -> None:
         """Tests that /sync returns the right value for the unread count (MSC2654)."""
 
         # Check that our own messages don't increase the unread count.
@@ -624,7 +638,7 @@ class UnreadMessagesTestCase(unittest.HomeserverTestCase):
         # Send a read receipt to tell the server we've read the latest event.
         channel = self.make_request(
             "POST",
-            f"/rooms/{self.room_id}/receipt/org.matrix.msc2285.read.private/{res['event_id']}",
+            f"/rooms/{self.room_id}/receipt/{receipt_type}/{res['event_id']}",
             {},
             access_token=self.tok,
         )
@@ -700,7 +714,7 @@ class UnreadMessagesTestCase(unittest.HomeserverTestCase):
         self._check_unread_count(5)
         res2 = self.helper.send(self.room_id, "hello", tok=self.tok2)
 
-        # Make sure both m.read and org.matrix.msc2285.read.private advance
+        # Make sure both m.read and m.read.private advance
         channel = self.make_request(
             "POST",
             f"/rooms/{self.room_id}/receipt/m.read/{res1['event_id']}",
@@ -712,16 +726,22 @@ class UnreadMessagesTestCase(unittest.HomeserverTestCase):
 
         channel = self.make_request(
             "POST",
-            f"/rooms/{self.room_id}/receipt/org.matrix.msc2285.read.private/{res2['event_id']}",
+            f"/rooms/{self.room_id}/receipt/{receipt_type}/{res2['event_id']}",
             {},
             access_token=self.tok,
         )
         self.assertEqual(channel.code, 200, channel.json_body)
         self._check_unread_count(0)
 
-    # We test for both receipt types that influence notification counts
-    @parameterized.expand([ReceiptTypes.READ, ReceiptTypes.READ_PRIVATE])
-    def test_read_receipts_only_go_down(self, receipt_type: ReceiptTypes) -> None:
+    # We test for all three receipt types that influence notification counts
+    @parameterized.expand(
+        [
+            ReceiptTypes.READ,
+            ReceiptTypes.READ_PRIVATE,
+            ReceiptTypes.UNSTABLE_READ_PRIVATE,
+        ]
+    )
+    def test_read_receipts_only_go_down(self, receipt_type: str) -> None:
         # Join the new user
         self.helper.join(room=self.room_id, user=self.user2, tok=self.tok2)
 
@@ -739,11 +759,11 @@ class UnreadMessagesTestCase(unittest.HomeserverTestCase):
         self.assertEqual(channel.code, 200, channel.json_body)
         self._check_unread_count(0)
 
-        # Make sure neither m.read nor org.matrix.msc2285.read.private make the
+        # Make sure neither m.read nor m.read.private make the
         # read receipt go up to an older event
         channel = self.make_request(
             "POST",
-            f"/rooms/{self.room_id}/receipt/org.matrix.msc2285.read.private/{res1['event_id']}",
+            f"/rooms/{self.room_id}/receipt/{receipt_type}/{res1['event_id']}",
             {},
             access_token=self.tok,
         )
diff --git a/tests/storage/test_receipts.py b/tests/storage/test_receipts.py
index b1a8f8bba7..191c957fb5 100644
--- a/tests/storage/test_receipts.py
+++ b/tests/storage/test_receipts.py
@@ -12,6 +12,8 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
+from parameterized import parameterized
+
 from synapse.api.constants import ReceiptTypes
 from synapse.types import UserID, create_requester
 
@@ -23,7 +25,7 @@ OUR_USER_ID = "@our:test"
 
 
 class ReceiptTestCase(HomeserverTestCase):
-    def prepare(self, reactor, clock, homeserver):
+    def prepare(self, reactor, clock, homeserver) -> None:
         super().prepare(reactor, clock, homeserver)
 
         self.store = homeserver.get_datastores().main
@@ -83,10 +85,15 @@ class ReceiptTestCase(HomeserverTestCase):
             )
         )
 
-    def test_return_empty_with_no_data(self):
+    def test_return_empty_with_no_data(self) -> None:
         res = self.get_success(
             self.store.get_receipts_for_user(
-                OUR_USER_ID, [ReceiptTypes.READ, ReceiptTypes.READ_PRIVATE]
+                OUR_USER_ID,
+                [
+                    ReceiptTypes.READ,
+                    ReceiptTypes.READ_PRIVATE,
+                    ReceiptTypes.UNSTABLE_READ_PRIVATE,
+                ],
             )
         )
         self.assertEqual(res, {})
@@ -94,7 +101,11 @@ class ReceiptTestCase(HomeserverTestCase):
         res = self.get_success(
             self.store.get_receipts_for_user_with_orderings(
                 OUR_USER_ID,
-                [ReceiptTypes.READ, ReceiptTypes.READ_PRIVATE],
+                [
+                    ReceiptTypes.READ,
+                    ReceiptTypes.READ_PRIVATE,
+                    ReceiptTypes.UNSTABLE_READ_PRIVATE,
+                ],
             )
         )
         self.assertEqual(res, {})
@@ -103,12 +114,19 @@ class ReceiptTestCase(HomeserverTestCase):
             self.store.get_last_receipt_event_id_for_user(
                 OUR_USER_ID,
                 self.room_id1,
-                [ReceiptTypes.READ, ReceiptTypes.READ_PRIVATE],
+                [
+                    ReceiptTypes.READ,
+                    ReceiptTypes.READ_PRIVATE,
+                    ReceiptTypes.UNSTABLE_READ_PRIVATE,
+                ],
             )
         )
         self.assertEqual(res, None)
 
-    def test_get_receipts_for_user(self):
+    @parameterized.expand(
+        [ReceiptTypes.READ_PRIVATE, ReceiptTypes.UNSTABLE_READ_PRIVATE]
+    )
+    def test_get_receipts_for_user(self, receipt_type: str) -> None:
         # Send some events into the first room
         event1_1_id = self.create_and_send_event(
             self.room_id1, UserID.from_string(OTHER_USER_ID)
@@ -126,14 +144,14 @@ class ReceiptTestCase(HomeserverTestCase):
         # Send private read receipt for the second event
         self.get_success(
             self.store.insert_receipt(
-                self.room_id1, ReceiptTypes.READ_PRIVATE, OUR_USER_ID, [event1_2_id], {}
+                self.room_id1, receipt_type, OUR_USER_ID, [event1_2_id], {}
             )
         )
 
         # Test we get the latest event when we want both private and public receipts
         res = self.get_success(
             self.store.get_receipts_for_user(
-                OUR_USER_ID, [ReceiptTypes.READ, ReceiptTypes.READ_PRIVATE]
+                OUR_USER_ID, [ReceiptTypes.READ, receipt_type]
             )
         )
         self.assertEqual(res, {self.room_id1: event1_2_id})
@@ -146,7 +164,7 @@ class ReceiptTestCase(HomeserverTestCase):
 
         # Test we get the latest event when we want only the public receipt
         res = self.get_success(
-            self.store.get_receipts_for_user(OUR_USER_ID, [ReceiptTypes.READ_PRIVATE])
+            self.store.get_receipts_for_user(OUR_USER_ID, [receipt_type])
         )
         self.assertEqual(res, {self.room_id1: event1_2_id})
 
@@ -169,17 +187,20 @@ class ReceiptTestCase(HomeserverTestCase):
         # Test new room is reflected in what the method returns
         self.get_success(
             self.store.insert_receipt(
-                self.room_id2, ReceiptTypes.READ_PRIVATE, OUR_USER_ID, [event2_1_id], {}
+                self.room_id2, receipt_type, OUR_USER_ID, [event2_1_id], {}
             )
         )
         res = self.get_success(
             self.store.get_receipts_for_user(
-                OUR_USER_ID, [ReceiptTypes.READ, ReceiptTypes.READ_PRIVATE]
+                OUR_USER_ID, [ReceiptTypes.READ, receipt_type]
             )
         )
         self.assertEqual(res, {self.room_id1: event1_2_id, self.room_id2: event2_1_id})
 
-    def test_get_last_receipt_event_id_for_user(self):
+    @parameterized.expand(
+        [ReceiptTypes.READ_PRIVATE, ReceiptTypes.UNSTABLE_READ_PRIVATE]
+    )
+    def test_get_last_receipt_event_id_for_user(self, receipt_type: str) -> None:
         # Send some events into the first room
         event1_1_id = self.create_and_send_event(
             self.room_id1, UserID.from_string(OTHER_USER_ID)
@@ -197,7 +218,7 @@ class ReceiptTestCase(HomeserverTestCase):
         # Send private read receipt for the second event
         self.get_success(
             self.store.insert_receipt(
-                self.room_id1, ReceiptTypes.READ_PRIVATE, OUR_USER_ID, [event1_2_id], {}
+                self.room_id1, receipt_type, OUR_USER_ID, [event1_2_id], {}
             )
         )
 
@@ -206,7 +227,7 @@ class ReceiptTestCase(HomeserverTestCase):
             self.store.get_last_receipt_event_id_for_user(
                 OUR_USER_ID,
                 self.room_id1,
-                [ReceiptTypes.READ, ReceiptTypes.READ_PRIVATE],
+                [ReceiptTypes.READ, receipt_type],
             )
         )
         self.assertEqual(res, event1_2_id)
@@ -222,7 +243,7 @@ class ReceiptTestCase(HomeserverTestCase):
         # Test we get the latest event when we want only the private receipt
         res = self.get_success(
             self.store.get_last_receipt_event_id_for_user(
-                OUR_USER_ID, self.room_id1, [ReceiptTypes.READ_PRIVATE]
+                OUR_USER_ID, self.room_id1, [receipt_type]
             )
         )
         self.assertEqual(res, event1_2_id)
@@ -248,14 +269,14 @@ class ReceiptTestCase(HomeserverTestCase):
         # Test new room is reflected in what the method returns
         self.get_success(
             self.store.insert_receipt(
-                self.room_id2, ReceiptTypes.READ_PRIVATE, OUR_USER_ID, [event2_1_id], {}
+                self.room_id2, receipt_type, OUR_USER_ID, [event2_1_id], {}
             )
         )
         res = self.get_success(
             self.store.get_last_receipt_event_id_for_user(
                 OUR_USER_ID,
                 self.room_id2,
-                [ReceiptTypes.READ, ReceiptTypes.READ_PRIVATE],
+                [ReceiptTypes.READ, receipt_type],
             )
         )
         self.assertEqual(res, event2_1_id)