diff --git a/error_13.go b/error_13.go
index c91b82d6..f1ec1d85 100644
--- a/error_13.go
+++ b/error_13.go
@@ -4,4 +4,5 @@ package gorm
 
 import "errors"
 
+// use go1.13 errors.Is to check is err is target error.
 var isError = errors.Is