diff --git a/src/api/api_comment.php b/src/api/api_comment.php
index 433cad3f86..25f68bf114 100644
--- a/src/api/api_comment.php
+++ b/src/api/api_comment.php
@@ -266,7 +266,7 @@ private function run_qreq(Qrequest $qreq) {
 
         if ($this->status === self::RESPONSE_REPLACED) {
             // report response replacement error
-            $jr = JsonResult::make_error(404, "<0>{uccmttype} was edited concurrently");
+            $jr = JsonResult::make_error(404, "<0>{$uccmttype} was edited concurrently");
             $jr["conflict"] = true;
         } else {
             $jr = new JsonResult($this->status, ["ok" => $this->status <= 299]);