diff --git a/libc/string/strchr.c b/libc/string/strchr.c
index 93cb250b0..29acca591 100644
--- a/libc/string/strchr.c
+++ b/libc/string/strchr.c
@@ -47,5 +47,5 @@ __strchr_chk(const char *p, int ch, size_t s_len)
 
 char *
 strchr(const char *p, int ch) {
-    return __strchr_chk(p, ch, (size_t) -1);
+    return __strchr_chk(p, ch, __BIONIC_FORTIFY_UNKNOWN_SIZE);
 }
diff --git a/libc/string/strrchr.c b/libc/string/strrchr.c
index 14f29c551..e709d498c 100644
--- a/libc/string/strrchr.c
+++ b/libc/string/strrchr.c
@@ -50,5 +50,5 @@ __strrchr_chk(const char *p, int ch, size_t s_len)
 char *
 strrchr(const char *p, int ch)
 {
-	return __strrchr_chk(p, ch, (size_t) -1);
+	return __strrchr_chk(p, ch, __BIONIC_FORTIFY_UNKNOWN_SIZE);
 }