diff --git a/specs/swml/calling/Methods/hangup/main.tsp b/specs/swml/calling/Methods/hangup/main.tsp
index f5ec9f2078..fcbebfa937 100644
--- a/specs/swml/calling/Methods/hangup/main.tsp
+++ b/specs/swml/calling/Methods/hangup/main.tsp
@@ -4,7 +4,7 @@ namespace SWML.Calling;
 model Hangup {
   @doc("End the call with an optional reason.")
   @summary("hangup")
-  hangup: {
+  hangup: null | {
     @doc("The reason for hanging up the call.")
     @example("busy")
     reason?: "hangup" | "busy" | "decline";
diff --git a/specs/swml/calling/tsp-output/@typespec/json-schema/SWMLObject.json b/specs/swml/calling/tsp-output/@typespec/json-schema/SWMLObject.json
index c4dc4311dd..0d9c60286b 100644
--- a/specs/swml/calling/tsp-output/@typespec/json-schema/SWMLObject.json
+++ b/specs/swml/calling/tsp-output/@typespec/json-schema/SWMLObject.json
@@ -580,32 +580,39 @@
             "type": "object",
             "properties": {
                 "hangup": {
-                    "type": "object",
-                    "properties": {
-                        "reason": {
-                            "anyOf": [
-                                {
-                                    "type": "string",
-                                    "const": "hangup"
-                                },
-                                {
-                                    "type": "string",
-                                    "const": "busy"
-                                },
-                                {
-                                    "type": "string",
-                                    "const": "decline"
+                    "anyOf": [
+                        {
+                            "type": "null"
+                        },
+                        {
+                            "type": "object",
+                            "properties": {
+                                "reason": {
+                                    "anyOf": [
+                                        {
+                                            "type": "string",
+                                            "const": "hangup"
+                                        },
+                                        {
+                                            "type": "string",
+                                            "const": "busy"
+                                        },
+                                        {
+                                            "type": "string",
+                                            "const": "decline"
+                                        }
+                                    ],
+                                    "examples": [
+                                        "busy"
+                                    ],
+                                    "description": "The reason for hanging up the call."
                                 }
-                            ],
-                            "examples": [
-                                "busy"
-                            ],
-                            "description": "The reason for hanging up the call."
+                            },
+                            "unevaluatedProperties": {
+                                "not": {}
+                            }
                         }
-                    },
-                    "unevaluatedProperties": {
-                        "not": {}
-                    },
+                    ],
                     "description": "End the call with an optional reason.",
                     "title": "hangup"
                 }