diff --git a/main.py b/main.py
index 18d316a6..5e9a6db5 100644
--- a/main.py
+++ b/main.py
@@ -75,6 +75,9 @@ def _send_flow_mods_from_request(self, dpid, command):
         else:
             switches = [self.controller.get_switch_by_dpid(dpid)]
 
+        if None in switches:
+            return jsonify({"reponse": "dpid not found"}), 404
+
         for switch in switches:
             serializer = self._get_flow_serializer(switch)
             flows = flows_dict.get('flows', [])