diff --git a/changelog.d/12410.bugfix b/changelog.d/12410.bugfix
new file mode 100644
index 0000000000..d042425d20
--- /dev/null
+++ b/changelog.d/12410.bugfix
@@ -0,0 +1 @@
+Fix a spec compliance issue where requests to the `/publicRooms` federation API would specify `limit` as a string.
\ No newline at end of file
diff --git a/synapse/federation/transport/client.py b/synapse/federation/transport/client.py
index d4b3cb3e98..66a41e45fc 100644
--- a/synapse/federation/transport/client.py
+++ b/synapse/federation/transport/client.py
@@ -509,7 +509,7 @@ class TransportLayerClient:
             if third_party_instance_id:
                 args["third_party_instance_id"] = (third_party_instance_id,)
             if limit:
-                args["limit"] = [limit]
+                args["limit"] = [str(limit)]
             if since_token:
                 args["since"] = [since_token]