diff --git a/changelog.d/6139.misc b/changelog.d/6139.misc
new file mode 100644
index 0000000000000000000000000000000000000000..d4b65e7af81fa44a6364c0ef79ec7e40f717610c
--- /dev/null
+++ b/changelog.d/6139.misc
@@ -0,0 +1 @@
+Log responder when responding to media request.
diff --git a/synapse/rest/media/v1/_base.py b/synapse/rest/media/v1/_base.py
index 5fefee4dde383c5867d890cceb1a6efde0eced7c..65bbf0007317e2d37f083675ddcd0d2839806398 100644
--- a/synapse/rest/media/v1/_base.py
+++ b/synapse/rest/media/v1/_base.py
@@ -195,7 +195,7 @@ def respond_with_responder(request, responder, media_type, file_size, upload_nam
         respond_404(request)
         return
 
-    logger.debug("Responding to media request with responder %s")
+    logger.debug("Responding to media request with responder %s", responder)
     add_file_headers(request, media_type, file_size, upload_name)
     try:
         with responder: