diff --git a/lib/Rest/HttpResponse.cpp b/lib/Rest/HttpResponse.cpp
index 584cf22a98..9367d744ac 100644
--- a/lib/Rest/HttpResponse.cpp
+++ b/lib/Rest/HttpResponse.cpp
@@ -227,6 +227,7 @@ HttpResponse::HttpResponseCode HttpResponse::responseCode (int code) {
 
     case TRI_ERROR_ARANGO_CONFLICT:
     case TRI_ERROR_ARANGO_GEO_INDEX_VIOLATED:
+    case TRI_ERROR_ARANGO_UNIQUE_CONSTRAINT_VIOLATED:
     case TRI_ERROR_CURSOR_BUSY:
       return CONFLICT;