diff --git a/libc/signal/sig_set.c b/libc/signal/sig_set.c
index b7fe7c603b..de0b27def3 100644
--- a/libc/signal/sig_set.c
+++ b/libc/signal/sig_set.c
@@ -115,7 +115,7 @@ CODE void (*sigset(int signo, CODE void (*func)(int signo)))(int signo)
   sigset_t set;
   int ret;
 
-  DEBUGASSERT(GOOD_SIGNO(signo) && func != NULL);
+  DEBUGASSERT(GOOD_SIGNO(signo) && func != SIG_ERR);
 
   (void)sigemptyset(&set);
   (void)sigaddset(&set, signo);
diff --git a/libc/signal/signal.c b/libc/signal/signal.c
index e7df89ce29..5830538297 100644
--- a/libc/signal/signal.c
+++ b/libc/signal/signal.c
@@ -76,8 +76,7 @@ CODE void (*signal(int signo, CODE void (*func)(int signo)))(int signo)
   struct sigaction oact;
   int ret;
 
-  DEBUGASSERT(GOOD_SIGNO(signo) && func != NULL);
-  DEBUGASSERT(func != SIG_ERR && func != SIG_HOLD);
+  DEBUGASSERT(GOOD_SIGNO(signo) && func != SIG_ERR && func != SIG_HOLD);
 
   /* Initialize the sigaction structure */