diff --git a/tests/headers/posix/strings_h.c b/tests/headers/posix/strings_h.c
index 0a2fa84..2051c8b 100644
--- a/tests/headers/posix/strings_h.c
+++ b/tests/headers/posix/strings_h.c
@@ -32,6 +32,10 @@
 
 static void strings_h() {
   FUNCTION(ffs, int (*f)(int));
+#if !defined(__GLIBC__)
+  FUNCTION(ffsl, int (*f)(long));
+  FUNCTION(ffsll, int (*f)(long long));
+#endif
   FUNCTION(strcasecmp, int (*f)(const char*, const char*));
   FUNCTION(strcasecmp_l, int (*f)(const char*, const char*, locale_t));
   FUNCTION(strncasecmp, int (*f)(const char*, const char*, size_t));