diff --git a/synapse/storage/devices.py b/synapse/storage/devices.py
index 6727861eb5..75c30abc28 100644
--- a/synapse/storage/devices.py
+++ b/synapse/storage/devices.py
@@ -115,12 +115,14 @@ class DeviceStore(SQLBaseStore):
         Returns:
             defer.Deferred
         """
-        return self._simple_delete_one(
+        self._simple_delete_one(
             table="devices",
             keyvalues={"user_id": user_id, "device_id": device_id},
             desc="delete_device",
         )
 
+        self.device_id_exists_cache.invalidate((user_id, device_id))
+
     def delete_devices(self, user_id, device_ids):
         """Deletes several devices.
 
@@ -130,13 +132,15 @@ class DeviceStore(SQLBaseStore):
         Returns:
             defer.Deferred
         """
-        return self._simple_delete_many(
+        self._simple_delete_many(
             table="devices",
             column="device_id",
             iterable=device_ids,
             keyvalues={"user_id": user_id},
             desc="delete_devices",
         )
+        for device_id in device_ids:
+            self.device_id_exists_cache.invalidate((user_id, device_id))
 
     def update_device(self, user_id, device_id, new_display_name=None):
         """Update a device.