diff --git a/sh/trap.c b/sh/trap.c
index 7cb5201..dcd76ac 100644
--- a/sh/trap.c
+++ b/sh/trap.c
@@ -100,7 +100,7 @@
 		p += 3;
 
 	for (i = 0; i < NSIG; ++i)
-		if (strcasecmp (p, sys_signame[i]) == 0)
+		if (sys_signame[i] && (strcasecmp (p, sys_signame[i]) == 0))
 			return i;
 	return -1;
 }