diff --git a/backend/fluksio/flow/nodes/http.py b/backend/fluksio/flow/nodes/http.py
index 9fbf12d..9ceba3d 100644
--- a/backend/fluksio/flow/nodes/http.py
+++ b/backend/fluksio/flow/nodes/http.py
@@ -301,7 +301,7 @@ class HttpNode(Node):
         :type params: dict
         :param kwargs: Pipeline data to send (from required messages).
         :type kwargs: Any
-        :returns: Response data if the endpoint returns JSON, None otherwise.
+        :returns: The reply's values for the declared output ports, or None.
         :rtype: dict | None
         """
         client = shared_client()
@@ -330,8 +330,13 @@ class HttpNode(Node):
             except Exception:
                 return None
             # Outputs are keyed by port, so only an object can be one. A bare
-            # scalar or list is a valid reply, just not something to publish.
-            return body if isinstance(body, dict) else None
+            # scalar or list is a valid reply, just not something to publish,
+            # and neither is a key no port declares: the reply is the
+            # endpoint's, and a `status` beside the values is common.
+            if not isinstance(body, dict):
+                return None
+            ports = {spec.port for spec in self.output_ports}
+            return {key: value for key, value in body.items() if key in ports} or None
 
         except httpx.HTTPStatusError as e:
             logger.error(
diff --git a/backend/tests/flow/test_senders.py b/backend/tests/flow/test_senders.py
index 1cbfbb8..e59cd6c 100644
--- a/backend/tests/flow/test_senders.py
+++ b/backend/tests/flow/test_senders.py
@@ -2,8 +2,10 @@
 
 import asyncio
 
+import httpx
+
 from fluksio.flow.messages import DType, MessageSpec
-from fluksio.flow.nodes import MqttNode
+from fluksio.flow.nodes import HttpNode, MqttNode
 from fluksio.flow.nodes.http import close_shared_client, shared_client
 
 
@@ -20,6 +22,28 @@ def test_http_senders_share_one_pooled_client():
     close_shared_client()
 
 
+def test_an_http_reply_keeps_only_the_declared_ports(monkeypatch):
+    """A `status` beside the value is the endpoint's business, not an error."""
+    reply = {"temp": 21.5, "status": "ok"}
+    client = httpx.Client(
+        transport=httpx.MockTransport(lambda _: httpx.Response(200, json=reply))
+    )
+    monkeypatch.setattr("fluksio.flow.nodes.http.shared_client", lambda: client)
+
+    def sender(*provides: MessageSpec) -> HttpNode:
+        node = HttpNode(
+            requires=[MessageSpec(name="setpoint", dtype=DType.FLOAT)],
+            provides=provides,
+            params={"url": "http://thermostat.test/set"},
+        )
+        node.assign_flow("heating", "thermostat")
+        return node
+
+    temp = MessageSpec(name="temp", dtype=DType.FLOAT)
+    assert sender(temp).execute({"heating.setpoint": 21.0}) == {"heating.temp": 21.5}
+    assert sender().execute({"heating.setpoint": 21.0}) is None
+
+
 def _sender() -> MqttNode:
     node = MqttNode(
         requires=[MessageSpec(name="setpoint", port="setpoint", dtype=DType.FLOAT)],
diff --git a/docs/reference/node-types.md b/docs/reference/node-types.md
index 0157174..ea57a43 100644
--- a/docs/reference/node-types.md
+++ b/docs/reference/node-types.md
@@ -63,7 +63,7 @@ The ports pick the direction: outputs only make a **listener**, inputs a
 **sender**. A listener is a **webhook**: the engine mounts a route at
 `/hooks/{flow}/{url}/{secret}` while the flow runs. A sender requests `url`
 and publishes a JSON object response on its outputs, one key per output port.
-A key no port declares fails the call, and a response that is not an object
+Keys no port declares are dropped, and a response that is not an object
 publishes nothing.
 
 | Setting | Default | Notes |