diff --git a/sanic/response/types.py b/sanic/response/types.py
index 3f93855d..d3c8cdb6 100644
--- a/sanic/response/types.py
+++ b/sanic/response/types.py
@@ -345,7 +345,7 @@ class JSONResponse(HTTPResponse):
         body: Optional[Any] = None,
         status: int = 200,
         headers: Optional[Union[Header, Dict[str, str]]] = None,
-        content_type: Optional[str] = None,
+        content_type: str = "application/json",
         dumps: Optional[Callable[..., str]] = None,
         **kwargs: Any,
     ):
diff --git a/tests/test_response_json.py b/tests/test_response_json.py
index c89dba42..aa1c61dd 100644
--- a/tests/test_response_json.py
+++ b/tests/test_response_json.py
@@ -213,3 +213,12 @@ def test_pop_list(json_app: Sanic):
 
     _, resp = json_app.test_client.get("/json-pop")
     assert resp.body == json_dumps(["b"]).encode()
+
+
+def test_json_response_class_sets_proper_content_type(json_app: Sanic):
+    @json_app.get("/json-class")
+    async def handler(request: Request):
+        return JSONResponse(JSON_BODY)
+
+    _, resp = json_app.test_client.get("/json-class")
+    assert resp.headers["content-type"] == "application/json"