diff --git a/libpthread/linuxthreads/signals.c b/libpthread/linuxthreads/signals.c
index c08125579..61b411aba 100644
--- a/libpthread/linuxthreads/signals.c
+++ b/libpthread/linuxthreads/signals.c
@@ -113,7 +113,7 @@ int __pthread_sigaction(int sig, const struct sigaction * act,
     newactp = NULL;
   if (__libc_sigaction(sig, newactp, oact) == -1)
     {
-      if (act)
+      if (act && (sig > 0 && sig < NSIG))
 	__sighandler[sig].old = (arch_sighandler_t) old;
       return -1;
     }