diff --git a/lib/server/socket.js b/lib/server/socket.js
index a489e5fc..5cd75ec5 100644
--- a/lib/server/socket.js
+++ b/lib/server/socket.js
@@ -264,6 +264,9 @@
             });
             
             cmd.on('error', Util.retFalse);
+            cmd.on('close', function (code) {
+                cmd = null;
+            });
         }
     }