diff --git a/vlib/v/tests/c_function_mut_param/code.c b/vlib/v/tests/c_function_mut_param/code.c
index d233a68851..bd778d7868 100644
--- a/vlib/v/tests/c_function_mut_param/code.c
+++ b/vlib/v/tests/c_function_mut_param/code.c
@@ -1,3 +1,3 @@
-void mut_arg(const byte *_key, size_t *val) {
+void mut_arg(const u8 *_key, size_t *val) {
 	*val = 5;
 }