diff --git a/changelog.d/12858.bugfix b/changelog.d/12858.bugfix
new file mode 100644
index 000000000..7a7ddc9a1
--- /dev/null
+++ b/changelog.d/12858.bugfix
@@ -0,0 +1 @@
+Fix [MSC3878](https://github.com/matrix-org/matrix-spec-proposals/pull/3787) rooms being omitted from room directory, room summary and space hierarchy responses.
diff --git a/scripts-dev/complement.sh b/scripts-dev/complement.sh
index ca476d9a5..3c472c576 100755
--- a/scripts-dev/complement.sh
+++ b/scripts-dev/complement.sh
@@ -45,7 +45,7 @@ docker build -t matrixdotorg/synapse -f "docker/Dockerfile" .
 
 extra_test_args=()
 
-test_tags="synapse_blacklist,msc2716,msc3030"
+test_tags="synapse_blacklist,msc2716,msc3030,msc3787"
 
 # If we're using workers, modify the docker files slightly.
 if [[ -n "$WORKERS" ]]; then
diff --git a/synapse/handlers/room_summary.py b/synapse/handlers/room_summary.py
index af83de319..1dd74912f 100644
--- a/synapse/handlers/room_summary.py
+++ b/synapse/handlers/room_summary.py
@@ -662,7 +662,8 @@ class RoomSummaryHandler:
         # The API doesn't return the room version so assume that a
         # join rule of knock is valid.
         if (
-            room.get("join_rules") in (JoinRules.PUBLIC, JoinRules.KNOCK)
+            room.get("join_rules")
+            in (JoinRules.PUBLIC, JoinRules.KNOCK, JoinRules.KNOCK_RESTRICTED)
             or room.get("world_readable") is True
         ):
             return True
diff --git a/synapse/storage/databases/main/room.py b/synapse/storage/databases/main/room.py
index ded15b92e..10f2ceb50 100644
--- a/synapse/storage/databases/main/room.py
+++ b/synapse/storage/databases/main/room.py
@@ -233,24 +233,23 @@ class RoomWorkerStore(CacheInvalidationWorkerStore):
                     UNION SELECT room_id from appservice_room_list
             """
 
-            sql = """
+            sql = f"""
                 SELECT
                     COUNT(*)
                 FROM (
-                    %(published_sql)s
+                    {published_sql}
                 ) published
                 INNER JOIN room_stats_state USING (room_id)
                 INNER JOIN room_stats_current USING (room_id)
                 WHERE
                     (
-                        join_rules = 'public' OR join_rules = '%(knock_join_rule)s'
+                        join_rules = '{JoinRules.PUBLIC}'
+                        OR join_rules = '{JoinRules.KNOCK}'
+                        OR join_rules = '{JoinRules.KNOCK_RESTRICTED}'
                         OR history_visibility = 'world_readable'
                     )
                     AND joined_members > 0
-            """ % {
-                "published_sql": published_sql,
-                "knock_join_rule": JoinRules.KNOCK,
-            }
+            """
 
             txn.execute(sql, query_args)
             return cast(Tuple[int], txn.fetchone())[0]
@@ -369,29 +368,29 @@ class RoomWorkerStore(CacheInvalidationWorkerStore):
         if where_clauses:
             where_clause = " AND " + " AND ".join(where_clauses)
 
-        sql = """
+        dir = "DESC" if forwards else "ASC"
+        sql = f"""
             SELECT
                 room_id, name, topic, canonical_alias, joined_members,
                 avatar, history_visibility, guest_access, join_rules
             FROM (
-                %(published_sql)s
+                {published_sql}
             ) published
             INNER JOIN room_stats_state USING (room_id)
             INNER JOIN room_stats_current USING (room_id)
             WHERE
                 (
-                    join_rules = 'public' OR join_rules = '%(knock_join_rule)s'
+                    join_rules = '{JoinRules.PUBLIC}'
+                    OR join_rules = '{JoinRules.KNOCK}'
+                    OR join_rules = '{JoinRules.KNOCK_RESTRICTED}'
                     OR history_visibility = 'world_readable'
                 )
                 AND joined_members > 0
-                %(where_clause)s
-            ORDER BY joined_members %(dir)s, room_id %(dir)s
-        """ % {
-            "published_sql": published_sql,
-            "where_clause": where_clause,
-            "dir": "DESC" if forwards else "ASC",
-            "knock_join_rule": JoinRules.KNOCK,
-        }
+                {where_clause}
+            ORDER BY
+                joined_members {dir},
+                room_id {dir}
+        """
 
         if limit is not None:
             query_args.append(limit)