--- a/main.c	Sat May 26 17:01:01 2012 +0200
+++ b/main.c	Sat May 26 17:04:22 2012 +0200
@@ -148,6 +148,8 @@
                 break;
             case 'N':
                 command_line.num_slots = atoi(optarg);
+                if (command_line.num_slots < 0)
+                    command_line.num_slots = 0;
                 break;
             case 'r':
                 command_line.request = c_REMOVEJOB;