diff --git a/changelog.d/14449.misc b/changelog.d/14449.misc
new file mode 100644
index 000000000..320c0b6fa
--- /dev/null
+++ b/changelog.d/14449.misc
@@ -0,0 +1 @@
+Fix type logic in TCP replication code that prevented correctly ignoring blank commands.
\ No newline at end of file
diff --git a/synapse/replication/tcp/protocol.py b/synapse/replication/tcp/protocol.py
index 7763ffb2d..56a5c2191 100644
--- a/synapse/replication/tcp/protocol.py
+++ b/synapse/replication/tcp/protocol.py
@@ -245,7 +245,7 @@ class BaseReplicationStreamProtocol(LineOnlyReceiver):
             self._parse_and_dispatch_line(line)
 
     def _parse_and_dispatch_line(self, line: bytes) -> None:
-        if line.strip() == "":
+        if line.strip() == b"":
             # Ignore blank lines
             return
 
diff --git a/synapse/storage/database.py b/synapse/storage/database.py
index 4717c9728..0dc44b246 100644
--- a/synapse/storage/database.py
+++ b/synapse/storage/database.py
@@ -569,15 +569,15 @@ class DatabasePool:
             retcols=["update_name"],
             desc="check_background_updates",
         )
-        updates = [x["update_name"] for x in updates]
+        background_update_names = [x["update_name"] for x in updates]
 
         for table, update_name in UNIQUE_INDEX_BACKGROUND_UPDATES.items():
-            if update_name not in updates:
+            if update_name not in background_update_names:
                 logger.debug("Now safe to upsert in %s", table)
                 self._unsafe_to_upsert_tables.discard(table)
 
         # If there's any updates still running, reschedule to run.
-        if updates:
+        if background_update_names:
             self._clock.call_later(
                 15.0,
                 run_as_background_process,