diff --git a/vm_dump.c b/vm_dump.c
index 4bc47898cf..5c56d61652 100644
--- a/vm_dump.c
+++ b/vm_dump.c
@@ -1054,7 +1054,7 @@ rb_vmdebug_stack_dump_all_threads(void)
     rb_thread_t *th = NULL;
 
     list_for_each(&vm->living_threads, th, vmlt_node) {
-	fprintf(stderr, "th: %p, native_id: %lx\n", th, (unsigned long)th->thread_id);
+	fprintf(stderr, "th: %p, native_id: %p\n", th, (void *)th->thread_id);
 	rb_vmdebug_stack_dump_raw(th, th->cfp);
     }
 }