diff --git a/pkg/function/args.go b/pkg/function/args.go
index 0e458f72a7..af4190cf83 100644
--- a/pkg/function/args.go
+++ b/pkg/function/args.go
@@ -23,7 +23,7 @@ import (
 // It will return an error if the argument type does not match the result type
 func Arg(args map[string]interface{}, argName string, result interface{}) error {
 	if val, ok := args[argName]; ok {
-		if err := mapstructure.Decode(val, result); err != nil {
+		if err := mapstructure.WeakDecode(val, result); err != nil {
 			return errors.Wrapf(err, "Failed to decode arg `%s`", argName)
 		}
 		return nil