diff --git a/synapse/http/site.py b/synapse/http/site.py
index c180a1d3231b..40f6c0489451 100644
--- a/synapse/http/site.py
+++ b/synapse/http/site.py
@@ -407,7 +407,10 @@ def _finished_processing(self) -> None:
 
         user_agent = get_request_user_agent(self, "-")
 
-        code = str(self.code)
+        # int(self.code) looks redundant, because self.code is already an int.
+        # But self.code might be an HTTPStatus (which inherits from int)---which has
+        # a different string representation. So ensure we really have an integer.
+        code = str(int(self.code))
         if not self.finished:
             # we didn't send the full response before we gave up (presumably because
             # the connection dropped)