diff --git a/libc/string/strrchr.c b/libc/string/strrchr.c
index 14f29c5..e709d49 100644
--- a/libc/string/strrchr.c
+++ b/libc/string/strrchr.c
@@ -50,5 +50,5 @@
 char *
 strrchr(const char *p, int ch)
 {
-	return __strrchr_chk(p, ch, (size_t) -1);
+	return __strrchr_chk(p, ch, __BIONIC_FORTIFY_UNKNOWN_SIZE);
 }