diff --git a/usr.bin/su/su.c b/usr.bin/su/su.c
index 76f76b61e64d..73d012a3460e 100644
--- a/usr.bin/su/su.c
+++ b/usr.bin/su/su.c
@@ -173,6 +173,8 @@ main(int argc, char *argv[])
 #ifdef USE_BSM_AUDIT
 	const char	*aerr;
 	au_id_t		 auid;
+
+	signal(SIGSYS, SIG_IGN);
 #endif
 
 	shell = class = cleanenv = NULL;