diff --git a/micro-activate.rs b/micro-activate.rs
index 73d7e3c..bb2dd24 100644
--- a/micro-activate.rs
+++ b/micro-activate.rs
@@ -98,7 +98,7 @@ fn main() -> Result<(), std::io::Error> {
     unsafe {
         assert_eq!(
             mount(
-                metadata_img.as_os_str().as_bytes().as_ptr(),
+                metadata_img.as_os_str().as_bytes().as_ptr() as *const c_char,
                 c"/run/etc.meta".as_ptr(),
                 c"erofs".as_ptr(),
                 MS_RDONLY | MS_NODEV | MS_NOSUID,