diff --git a/starlette/responses.py b/starlette/responses.py
index 26d730540..577d1bb04 100644
--- a/starlette/responses.py
+++ b/starlette/responses.py
@@ -174,6 +174,16 @@ class PlainTextResponse(Response):
 class JSONResponse(Response):
     media_type = "application/json"
 
+    def __init__(
+        self,
+        content: typing.Any,
+        status_code: int = 200,
+        headers: dict = None,
+        media_type: str = None,
+        background: BackgroundTask = None,
+    ) -> None:
+        super().__init__(content, status_code, headers, media_type, background)
+
     def render(self, content: typing.Any) -> bytes:
         return json.dumps(
             content,
diff --git a/tests/test_responses.py b/tests/test_responses.py
index e2337bdca..38aea5761 100644
--- a/tests/test_responses.py
+++ b/tests/test_responses.py
@@ -44,6 +44,7 @@ async def app(scope, receive, send):
     client = test_client_factory(app)
     response = client.get("/")
     assert response.json() is None
+    assert response.content == b"null"
 
 
 def test_redirect_response(test_client_factory):
@@ -330,7 +331,9 @@ def test_empty_response(test_client_factory):
     app = Response()
     client: TestClient = test_client_factory(app)
     response = client.get("/")
+    assert response.content == b""
     assert response.headers["content-length"] == "0"
+    assert "content-type" not in response.headers
 
 
 def test_empty_204_response(test_client_factory):