diff --git a/changelog.d/10727.misc b/changelog.d/10727.misc
new file mode 100644
index 000000000..63fe6e5c7
--- /dev/null
+++ b/changelog.d/10727.misc
@@ -0,0 +1 @@
+Do not include rooms with unknown room versions in the spaces summary results.
diff --git a/synapse/handlers/room_summary.py b/synapse/handlers/room_summary.py
index d1b6f3253..4bc9c73e6 100644
--- a/synapse/handlers/room_summary.py
+++ b/synapse/handlers/room_summary.py
@@ -28,7 +28,14 @@ from synapse.api.constants import (
     Membership,
     RoomTypes,
 )
-from synapse.api.errors import AuthError, Codes, NotFoundError, StoreError, SynapseError
+from synapse.api.errors import (
+    AuthError,
+    Codes,
+    NotFoundError,
+    StoreError,
+    SynapseError,
+    UnsupportedRoomVersionError,
+)
 from synapse.events import EventBase
 from synapse.events.utils import format_event_for_client_v2
 from synapse.types import JsonDict
@@ -814,7 +821,12 @@ class RoomSummaryHandler:
             logger.info("room %s is unknown, omitting from summary", room_id)
             return False
 
-        room_version = await self._store.get_room_version(room_id)
+        try:
+            room_version = await self._store.get_room_version(room_id)
+        except UnsupportedRoomVersionError:
+            # If a room with an unsupported room version is encountered, ignore
+            # it to avoid breaking the entire summary response.
+            return False
 
         # Include the room if it has join rules of public or knock.
         join_rules_event_id = state_ids.get((EventTypes.JoinRules, ""))
diff --git a/tests/handlers/test_room_summary.py b/tests/handlers/test_room_summary.py
index 449ba89e5..d3d0bf1ac 100644
--- a/tests/handlers/test_room_summary.py
+++ b/tests/handlers/test_room_summary.py
@@ -581,6 +581,31 @@ class SpaceSummaryTestCase(unittest.HomeserverTestCase):
         ]
         self._assert_hierarchy(result, expected)
 
+    def test_unknown_room_version(self):
+        """
+        If an room with an unknown room version is encountered it should not cause
+        the entire summary to skip.
+        """
+        # Poke the database and update the room version to an unknown one.
+        self.get_success(
+            self.hs.get_datastores().main.db_pool.simple_update(
+                "rooms",
+                keyvalues={"room_id": self.room},
+                updatevalues={"room_version": "unknown-room-version"},
+                desc="updated-room-version",
+            )
+        )
+
+        result = self.get_success(self.handler.get_space_summary(self.user, self.space))
+        # The result should have only the space, along with a link from space -> room.
+        expected = [(self.space, [self.room])]
+        self._assert_rooms(result, expected)
+
+        result = self.get_success(
+            self.handler.get_room_hierarchy(self.user, self.space)
+        )
+        self._assert_hierarchy(result, expected)
+
     def test_fed_complex(self):
         """
         Return data over federation and ensure that it is handled properly.