diff --git a/bindings/mqtt/0.2.0/server.json b/bindings/mqtt/0.2.0/server.json
index cbc002a6..28f8d800 100644
--- a/bindings/mqtt/0.2.0/server.json
+++ b/bindings/mqtt/0.2.0/server.json
@@ -6,7 +6,7 @@
   "type": "object",
   "additionalProperties": false,
   "patternProperties": {
-    "^x-[\\w\\d\\.\\-\\_]+$": {
+    "^x-[\\w\\d\\.\\x2d_]+$": {
       "$ref": "http://asyncapi.com/definitions/3.0.0/specificationExtension.json"
     }
   },