diff --git a/src/a2a/compat/v0_3/jsonrpc_adapter.py b/src/a2a/compat/v0_3/jsonrpc_adapter.py
index 04df1d0d0..2263f336b 100644
--- a/src/a2a/compat/v0_3/jsonrpc_adapter.py
+++ b/src/a2a/compat/v0_3/jsonrpc_adapter.py
@@ -31,7 +31,7 @@
     InternalError as CoreInternalError,
 )
 from a2a.server.jsonrpc_models import (
-    InvalidRequestError as CoreInvalidRequestError,
+    InvalidParamsError as CoreInvalidParamsError,
 )
 from a2a.server.jsonrpc_models import (
     JSONRPCError as CoreJSONRPCError,
@@ -128,7 +128,7 @@ async def handle_request(
 
                 return self._generate_error_response(
                     request_id,
-                    CoreInvalidRequestError(data=str(e)),
+                    CoreInvalidParamsError(data=str(e)),
                 )
 
             call_context = self._context_builder.build(request)
diff --git a/tests/compat/v0_3/test_jsonrpc_app_compat.py b/tests/compat/v0_3/test_jsonrpc_app_compat.py
index aec4a56ee..833f6c607 100644
--- a/tests/compat/v0_3/test_jsonrpc_app_compat.py
+++ b/tests/compat/v0_3/test_jsonrpc_app_compat.py
@@ -205,6 +205,25 @@ def test_get_task_not_found_v03_compat(
     assert data['error']['message'] == 'Task not found'
 
 
+def test_invalid_params_v03_compat(
+    client: TestClient, mock_handler: AsyncMock
+) -> None:
+    request_payload = {
+        'jsonrpc': '2.0',
+        'id': '7',
+        'method': 'message/send',
+        'params': {'message': {'messageId': 'req', 'role': 'user'}},
+    }
+
+    response = client.post('/', json=request_payload)
+    assert response.status_code == 200
+    data = response.json()
+
+    assert data['id'] == '7'
+    assert data['error']['code'] == -32602
+    mock_handler.on_message_send.assert_not_called()
+
+
 @pytest.mark.parametrize(
     ('error', 'expected_code'),
     [