diff --git a/arg_parser/parser.go b/arg_parser/parser.go
index c99f9dd..e7cbe74 100644
--- a/arg_parser/parser.go
+++ b/arg_parser/parser.go
@@ -217,7 +217,7 @@ func stringParser(ctx context.Context, scope types.Scope,
 		return fmt.Sprintf("%v", arg), nil
 
 	default:
-		return fmt.Sprintf("%s", arg), nil
+		return fmt.Sprintf("%v", arg), nil
 	}
 }
 
diff --git a/functions/functions.go b/functions/functions.go
index 57d87a5..4abf70d 100644
--- a/functions/functions.go
+++ b/functions/functions.go
@@ -194,11 +194,15 @@ func (self _EncodeFunction) Call(
 	switch t := arg.String.(type) {
 	case string:
 		arg_string = t
+
 	case []byte:
 		arg_string = string(t)
 
+	case error:
+		return t.Error()
+
 	case fmt.Stringer:
-		arg_string = fmt.Sprintf("%s", t)
+		arg_string = t.String()
 
 	default:
 		arg_string = fmt.Sprintf("%v", t)