diff --git a/pkg/stdlib/io/fs/write.go b/pkg/stdlib/io/fs/write.go
index d8c04117..2c159d56 100644
--- a/pkg/stdlib/io/fs/write.go
+++ b/pkg/stdlib/io/fs/write.go
@@ -144,7 +144,7 @@ func parseWriteMode(s string) (int, error) {
 		flag |= os.O_TRUNC
 
 	default:
-		return 0, core.Errorf(
+		return -1, core.Errorf(
 			core.ErrInvalidArgument,
 			"invalid mode `%s`", s,
 		)