diff --git a/mqtt/json_schemas/operation.json b/mqtt/json_schemas/operation.json
index 5f873953..fc1b66b8 100644
--- a/mqtt/json_schemas/operation.json
+++ b/mqtt/json_schemas/operation.json
@@ -13,6 +13,7 @@
   "properties": {
     "qos": {
       "type": "integer",
+      "enum": [0,1,2],
       "description": "Defines the Quality of Service (QoS) levels for the message flow between client and server. Its value MUST be either 0 (At most once delivery), 1 (At least once delivery), or 2 (Exactly once delivery)."
     },
     "retain": {