diff --git a/freqtrade/rpc/rpc.py b/freqtrade/rpc/rpc.py
index 14048da4f..ddf6018ad 100644
--- a/freqtrade/rpc/rpc.py
+++ b/freqtrade/rpc/rpc.py
@@ -822,10 +822,10 @@ class RPC:
             ).first()
             if not trade:
                 logger.warning('cancel_open_order: Invalid trade_id received.')
-                raise RPCException('Invalid trade_id')
+                raise RPCException('Invalid trade_id.')
             if not trade.open_order_id:
                 logger.warning('cancel_open_order: No open order for trade_id.')
-                raise RPCException('No open order for trade_id')
+                raise RPCException('No open order for trade_id.')
 
             try:
                 order = self._freqtrade.exchange.fetch_order(trade.open_order_id, trade.pair)
diff --git a/tests/rpc/test_rpc_apiserver.py b/tests/rpc/test_rpc_apiserver.py
index 60c88ac0f..4d06811ed 100644
--- a/tests/rpc/test_rpc_apiserver.py
+++ b/tests/rpc/test_rpc_apiserver.py
@@ -720,6 +720,10 @@ def test_api_delete_open_order(botclient, mocker, fee, markets, ticker, is_short
         cancel_stoploss_order=stoploss_mock,
     )
 
+    rc = client_delete(client, f"{BASE_URI}/trades/10/open-order")
+    assert_response(rc, 502)
+    assert 'Invalid trade_id.' in rc.json()['error']
+
     create_mock_trades(fee, is_short=is_short)
 
     trades = Trade.query.all()