diff --git a/scripts-dev/mypy_synapse_plugin.py b/scripts-dev/mypy_synapse_plugin.py
index 6592a4a6b7..4830c45432 100644
--- a/scripts-dev/mypy_synapse_plugin.py
+++ b/scripts-dev/mypy_synapse_plugin.py
@@ -22,7 +22,13 @@ import mypy.types
 from mypy.erasetype import remove_instance_last_known_values
 from mypy.errorcodes import ErrorCode
 from mypy.nodes import ARG_NAMED_OPT, TempNode, Var
-from mypy.plugin import FunctionSigContext, MethodSigContext, Plugin
+from mypy.plugin import (
+    FunctionSigContext,
+    MethodSigContext,
+    Plugin,
+    AttributeContext,
+    CheckerPluginInterface,
+)
 from mypy.typeops import bind_self
 from mypy.types import (
     AnyType,
@@ -56,6 +62,15 @@ class SynapsePlugin(Plugin):
 
         return None
 
+    def get_attribute_hook(
+        self, fullname: str
+    ) -> Optional[Callable[[AttributeContext], mypy.types.Type]]:
+        # Anything in synapse could be wrapped with the cached decorator, but
+        # we know that anything else is *not*.
+        if fullname.startswith("synapse."):
+            return cached_function_method_attribute
+        return None
+
 
 def _get_true_return_type(signature: CallableType) -> mypy.types.Type:
     """
@@ -79,6 +94,26 @@ def _get_true_return_type(signature: CallableType) -> mypy.types.Type:
 
 
 def cached_function_method_signature(ctx: MethodSigContext) -> CallableType:
+    return _unwrap_cached_decoratored_function(ctx.default_signature, ctx.api)
+
+
+def cached_function_method_attribute(ctx: AttributeContext) -> mypy.types.Type:
+    if isinstance(ctx.default_attr_type, Instance):
+        if (
+            ctx.default_attr_type.type.fullname
+            == "synapse.util.caches.descriptors.CachedFunction"
+        ):
+            # Unwrap the wrapped function.
+            return _unwrap_cached_decoratored_function(
+                ctx.default_attr_type.args[0], ctx.api
+            )
+
+    return ctx.default_attr_type
+
+
+def _unwrap_cached_decoratored_function(
+    wrapped_signature: CallableType, api: CheckerPluginInterface
+) -> CallableType:
     """Fixes the `CachedFunction.__call__` signature to be correct.
 
     It already has *almost* the correct signature, except:
@@ -90,12 +125,12 @@ def cached_function_method_signature(ctx: MethodSigContext) -> CallableType:
     """
 
     # 1. Mark this as a bound function signature.
-    signature: CallableType = bind_self(ctx.default_signature)
+    signature: CallableType = bind_self(wrapped_signature)
 
     # 2. Remove any "cache_context" args.
     #
     # Note: We should be only doing this if `cache_context=True` is set, but if
-    # it isn't then the code will raise an exception when its called anyway, so
+    # it isn't then the code will raise an exception when it's called anyway, so
     # it's not the end of the world.
     context_arg_index = None
     for idx, name in enumerate(signature.arg_names):
@@ -125,7 +160,7 @@ def cached_function_method_signature(ctx: MethodSigContext) -> CallableType:
                 arg_kinds=[],
                 arg_names=[],
                 ret_type=NoneType(),
-                fallback=ctx.api.named_generic_type("builtins.function", []),
+                fallback=api.named_generic_type("builtins.function", []),
             ),
         ]
     )
@@ -137,12 +172,12 @@ def cached_function_method_signature(ctx: MethodSigContext) -> CallableType:
     # 4. Ensure the return type is a Deferred.
     ret_arg = _get_true_return_type(signature)
 
-    # This should be able to use ctx.api.named_generic_type, but that doesn't seem
+    # This should be able to use api.named_generic_type, but that doesn't seem
     # to find the correct symbol for anything more than 1 module deep.
     #
     # modules is not part of CheckerPluginInterface. The following is a combination
     # of TypeChecker.named_generic_type and TypeChecker.lookup_typeinfo.
-    sym = ctx.api.modules["twisted.internet.defer"].names.get("Deferred")  # type: ignore[attr-defined]
+    sym = api.modules["twisted.internet.defer"].names.get("Deferred")  # type: ignore[attr-defined]
     ret_type = Instance(sym.node, [remove_instance_last_known_values(ret_arg)])
 
     signature = signature.copy_modified(
diff --git a/synapse/util/async_helpers.py b/synapse/util/async_helpers.py
index 8a55e4e41d..9360daff2b 100644
--- a/synapse/util/async_helpers.py
+++ b/synapse/util/async_helpers.py
@@ -395,9 +395,9 @@ def gather_results(
 
 
 def gather_results(  # type: ignore[misc]
-    deferredList: Tuple["defer.Deferred[T1]", ...],
+    deferredList: Tuple["defer.Deferred[Any]", ...],
     consumeErrors: bool = False,
-) -> "defer.Deferred[Tuple[T1, ...]]":
+) -> "defer.Deferred[Tuple[Any, ...]]":
     """Combines a tuple of `Deferred`s into a single `Deferred`.
 
     Wraps `defer.gatherResults` to provide type annotations that support heterogenous