Index: fileio.c
--- fileio.c.orig
+++ fileio.c
@@ -779,7 +779,7 @@ char *cmd;
 #ifdef SIGPIPE
       signal(SIGPIPE, SIG_DFL);
 #endif
-      execl("/bin/sh", "sh", "-c", cmd, 0);
+      execl("/bin/sh", "sh", "-c", cmd, NULL);
       Panic(errno, "/bin/sh");
     default:
       break;