diff --git a/synapse/push/bulk_push_rule_evaluator.py b/synapse/push/bulk_push_rule_evaluator.py
index 25f2fb9da..1e5c4b073 100644
--- a/synapse/push/bulk_push_rule_evaluator.py
+++ b/synapse/push/bulk_push_rule_evaluator.py
@@ -87,13 +87,13 @@ def evaluator_for_event(event, hs, store):
     all_in_room = yield store.get_users_in_room(room_id)
     all_in_room = set(all_in_room)
 
-    receipts = yield store.get_receipts_for_room(room_id, "m.read")
+    users_with_receipts = yield store.get_users_with_read_receipts_in_room(room_id)
 
     # any users with pushers must be ours: they have pushers
     user_ids = set(users_with_pushers)
-    for r in receipts:
-        if hs.is_mine_id(r['user_id']) and r['user_id'] in all_in_room:
-            user_ids.add(r['user_id'])
+    for uid in users_with_receipts:
+        if hs.is_mine_id(uid) and uid in all_in_room:
+            user_ids.add(uid)
 
     # if this event is an invite event, we may need to run rules for the user
     # who's been invited, otherwise they won't get told they've been invited
diff --git a/synapse/storage/receipts.py b/synapse/storage/receipts.py
index fdcf28f3e..964f30dff 100644
--- a/synapse/storage/receipts.py
+++ b/synapse/storage/receipts.py
@@ -34,6 +34,26 @@ class ReceiptsStore(SQLBaseStore):
             "ReceiptsRoomChangeCache", self._receipts_id_gen.get_current_token()
         )
 
+    @cachedInlineCallbacks()
+    def get_users_with_read_receipts_in_room(self, room_id):
+        receipts = yield self.get_receipts_for_room(room_id, "m.read")
+        defer.returnValue(set(r['user_id'] for r in receipts))
+
+    def _invalidate_get_users_with_receipts_in_room(self, room_id, receipt_type,
+                                                    user_id):
+        if receipt_type != "m.read":
+            return
+
+        # Returns an ObservableDeferred
+        res = self.get_users_with_read_receipts_in_room.cache.get((room_id,), None)
+
+        if res and res.called and user_id in res.result:
+            # We'd only be adding to the set, so no point invalidating if the
+            # user is already there
+            return
+
+        self.get_users_with_read_receipts_in_room.invalidate((room_id,))
+
     @cached(num_args=2)
     def get_receipts_for_room(self, room_id, receipt_type):
         return self._simple_select_list(
@@ -228,6 +248,10 @@ class ReceiptsStore(SQLBaseStore):
         txn.call_after(
             self.get_receipts_for_room.invalidate, (room_id, receipt_type)
         )
+        txn.call_after(
+            self._invalidate_get_users_with_receipts_in_room,
+            room_id, receipt_type, user_id,
+        )
         txn.call_after(
             self.get_receipts_for_user.invalidate, (user_id, receipt_type)
         )
@@ -373,6 +397,10 @@ class ReceiptsStore(SQLBaseStore):
         txn.call_after(
             self.get_receipts_for_room.invalidate, (room_id, receipt_type)
         )
+        txn.call_after(
+            self._invalidate_get_users_with_receipts_in_room,
+            room_id, receipt_type, user_id,
+        )
         txn.call_after(
             self.get_receipts_for_user.invalidate, (user_id, receipt_type)
         )