diff --git a/tests/headers/posix/signal_h.c b/tests/headers/posix/signal_h.c
index 82751f4..3b50fb9 100644
--- a/tests/headers/posix/signal_h.c
+++ b/tests/headers/posix/signal_h.c
@@ -75,6 +75,10 @@
   i = SIGRTMIN;
   i = SIGRTMAX;
 
+#if !defined(__GLIBC__)  // Our glibc is too old.
+  MACRO(SIG2STR_MAX);
+#endif
+
   MACRO(SIGABRT);
   MACRO(SIGALRM);
   MACRO(SIGBUS);