diff --git a/owlps-client/owlps-client.c b/owlps-client/owlps-client.c
index f9d7c2e..1a0aef1 100644
--- a/owlps-client/owlps-client.c
+++ b/owlps-client/owlps-client.c
@@ -134,9 +134,12 @@ void parse_main_options(int argc, char **argv)
           strncpy(options.iface, optarg, IFNAMSIZ + 1) ;
           break ;
         case 'l' :
-          /* Facultative getopt options does not handle separated
-           * values (like -l <port>) */
-          if (optarg == 0)
+          /* Facultative getopt options do not handle separated values
+           * (like -l <port>), so we have to test separately.
+           */
+          if (optarg) // We got an option like -l<port>, it's OK
+            options.listening_port = strtoul(optarg, NULL, 0) ;
+          else // We got -l alone or -l <port>
             {
               /* If we are at the end of the string, or the next optind
                * is an option, we have -l without a port number */
@@ -151,8 +154,6 @@ void parse_main_options(int argc, char **argv)
                   optind++ ;
                 }
             }
-          else // We got an option like -l<port>, it's OK
-            options.listening_port = strtoul(optarg, NULL, 0) ;
           break ;
         case 'n' :
           options.nb_pkt = strtoul(optarg, NULL, 0) ;