diff --git a/src/github.com/matrix-org/dendrite/mediaapi/writers/download.go b/src/github.com/matrix-org/dendrite/mediaapi/writers/download.go
index f087bc63f..4a578af5f 100644
--- a/src/github.com/matrix-org/dendrite/mediaapi/writers/download.go
+++ b/src/github.com/matrix-org/dendrite/mediaapi/writers/download.go
@@ -144,6 +144,7 @@ func Download(w http.ResponseWriter, req *http.Request, origin types.ServerName,
 						Code: 500,
 						JSON: jsonerror.Unknown(fmt.Sprintf("File with media ID %q could not be downloaded from %q", r.MediaMetadata.MediaID, r.MediaMetadata.Origin)),
 					}, logger)
+					activeRemoteRequests.Unlock()
 					return
 				}
 				logger.WithFields(log.Fields{