diff --git a/clientapi/routing/redaction.go b/clientapi/routing/redaction.go
index c7af20e29..230c96d28 100644
--- a/clientapi/routing/redaction.go
+++ b/clientapi/routing/redaction.go
@@ -77,6 +77,7 @@ func SendRedaction(
 	// if user is member of room, and sender ID is nil, then this user doesn't have a pseudo ID for some reason,
 	// which is unexpected.
 	if senderID == nil {
+		util.GetLogger(req.Context()).WithField("userID", *deviceUserID).WithField("roomID", roomID).Error("missing sender ID for user, despite having membership")
 		return util.JSONResponse{
 			Code: http.StatusInternalServerError,
 			JSON: spec.Unknown("internal server error"),