diff --git a/tests/test_extends.py b/tests/test_extends.py
index ce4662b..daab3c5 100644
--- a/tests/test_extends.py
+++ b/tests/test_extends.py
@@ -17,3 +17,6 @@ def test_extend_init():
 def test_service_init():
     with pytest.raises(ValueError, match=r"Both image and extends are not defined in service 'frontend', aborting."):
         Service(name='frontend')
+        
+    with pytest.raises(ValueError, match=r"Only one of image and extends can be defined in service '{name}', aborting."):
+        Service(name='frontend', image='image', extends=Extends(service_name='frontend', from_file='tests/in/000001.yaml'))