diff --git a/lib/api/2011-02-01/configuration.js b/lib/api/2011-02-01/configuration.js
index <HASH>..<HASH> 100644
--- a/lib/api/2011-02-01/configuration.js
+++ b/lib/api/2011-02-01/configuration.js
@@ -416,7 +416,7 @@ handlers.DeleteIndexField = function(context, request, response, config) {
     });
   } catch(error) {
     if (error.isValidationError && error.isMultiplexed)
-      validationErrors = error.messages.concat(validationErrors);
+      validationErrors = validationErrors.concat(error.messages);
     else
       throw error;
   }
@@ -440,7 +440,7 @@ handlers.DeleteIndexField = function(context, request, response, config) {
     });
   } catch(error) {
     if (error.isValidationError && error.isMultiplexed) {
-      validationErrors = error.messages.concat(validationErrors);
+      validationErrors = validationErrors.concat(error.messages);
     } else {
       assertNoOtherError();
       throw error;
Report domain name validation error before index field validation error for DeleteIndexField