diff --git a/libcbs/src/bishengc_safety/bishengc_safety.cbs b/libcbs/src/bishengc_safety/bishengc_safety.cbs
index d9465fd53bc830550f099fdf485379e810ed5dce..a02b49d54204b209adffa7b4967e681942a777cd 100644
--- a/libcbs/src/bishengc_safety/bishengc_safety.cbs
+++ b/libcbs/src/bishengc_safety/bishengc_safety.cbs
@@ -63,7 +63,7 @@ safe void bsc_refcell_immut_borrow_failed(void) {
     }
 }
 
-safe void safe_free(void * owned p) {
+safe void safe_free(void * _Nullable owned p) {
 	unsafe {
 		free((void *)p);
 	}