diff --git a/nucliadb/src/nucliadb/reader/api/v1/resource.py b/nucliadb/src/nucliadb/reader/api/v1/resource.py
index a11ad49a40..909eed1858 100644
--- a/nucliadb/src/nucliadb/reader/api/v1/resource.py
+++ b/nucliadb/src/nucliadb/reader/api/v1/resource.py
@@ -398,9 +398,10 @@ async def _get_resource_field(
                 raise HTTPException(status_code=404, detail="Resource does not exist")
 
         resource = ORMResource(txn, storage, kbid, rid)
+        if not await resource.field_exists(pb_field_id, field_id):
+            raise HTTPException(status_code=404, detail="Resource field does not exist")
+
         field = await resource.get_field(field_id, pb_field_id, load=True)
-        if field is None:
-            raise HTTPException(status_code=404, detail="Knowledge Box does not exist")
 
         resource_field = ResourceField(field_id=field_id, field_type=field_type)
 
diff --git a/nucliadb/tests/nucliadb/integration/test_conversation.py b/nucliadb/tests/nucliadb/integration/test_conversation.py
index f6f3d22c23..d4fc1fb85d 100644
--- a/nucliadb/tests/nucliadb/integration/test_conversation.py
+++ b/nucliadb/tests/nucliadb/integration/test_conversation.py
@@ -884,3 +884,85 @@ async def _test_semantic_search(message_text: str, message_id: str, message_vect
     # New message is searchable too
     await _test_keyword_search(new_message_text, new_message_id)
     await _test_semantic_search(new_message_text, new_message_id, new_message_vector)
+
+
+@pytest.mark.deploy_modes("standalone")
+async def test_append_messages_to_non_existent_conversation_field_creates_it(
+    nucliadb_writer: AsyncClient,
+    nucliadb_reader: AsyncClient,
+    standalone_knowledgebox: str,
+):
+    """Test that appending messages to a non-existent conversation field creates it."""
+    kbid = standalone_knowledgebox
+
+    # Create a resource without any conversation field
+    resp = await nucliadb_writer.post(
+        f"/kb/{kbid}/resources",
+        json={
+            "slug": "test_resource",
+            "title": "Test Resource",
+        },
+    )
+    assert resp.status_code == 201
+    rid = resp.json()["uuid"]
+
+    # Try to get the conversation field before appending - should fail
+    resp = await nucliadb_reader.get(
+        f"/kb/{kbid}/resource/{rid}/conversation/new_conversation",
+        params={"page": 1},
+    )
+    assert resp.status_code == 404
+
+    # Append messages to a non-existent conversation field
+    resp = await nucliadb_writer.put(
+        f"/kb/{kbid}/resource/{rid}/conversation/new_conversation/messages",
+        json=[
+            {
+                "to": ["assistant"],
+                "who": "user",
+                "timestamp": datetime.now().isoformat(),
+                "content": {"text": "Hello, how are you?"},
+                "ident": "1",
+                "type": MessageType.QUESTION.value,
+            },
+            {
+                "to": ["user"],
+                "who": "assistant",
+                "timestamp": datetime.now().isoformat(),
+                "content": {"text": "I'm doing well, thank you!"},
+                "ident": "2",
+                "type": MessageType.ANSWER.value,
+            },
+        ],
+    )
+    assert resp.status_code == 200
+    assert "seqid" in resp.json()
+
+    # Get the conversation field and verify the messages were added
+    resp = await nucliadb_reader.get(
+        f"/kb/{kbid}/resource/{rid}/conversation/new_conversation",
+        params={"page": 1, "show": ["value"]},
+    )
+    assert resp.status_code == 200
+    field_resp = ResourceField.model_validate(resp.json())
+    msgs = field_resp.value["messages"]  # type: ignore
+    assert len(msgs) == 2
+    assert msgs[0]["ident"] == "1"
+    assert msgs[0]["who"] == "user"
+    assert msgs[0]["content"]["text"] == "Hello, how are you?"
+    assert msgs[1]["ident"] == "2"
+    assert msgs[1]["who"] == "assistant"
+    assert msgs[1]["content"]["text"] == "I'm doing well, thank you!"
+
+    # Verify the field exists in the resource summary
+    resp = await nucliadb_reader.get(
+        f"/kb/{kbid}/resource/{rid}",
+        params={"show": ["values"]},
+    )
+    assert resp.status_code == 200
+    res_resp = ResponseResponse.model_validate(resp.json())
+    assert "new_conversation" in res_resp.data.conversations  # type: ignore
+    conv_field = res_resp.data.conversations["new_conversation"]  # type: ignore
+    assert conv_field.value is not None
+    assert conv_field.value.total == 2
+    assert conv_field.value.pages == 1