diff --git a/digid_eherkenning/mock/conf.py b/digid_eherkenning/mock/conf.py
index 85dc7c5..b1396df 100644
--- a/digid_eherkenning/mock/conf.py
+++ b/digid_eherkenning/mock/conf.py
@@ -52,7 +52,9 @@ def should_validate_idp_callback_urls() -> bool:
     """
     Whether to validate that the `next_url` and `cancel_urls` are safe
     """
-    flag = getattr(settings, "DIGID_MOCK_IDP_VALIDATE_CALLBACK_URLS", settings.DEBUG)
+    flag = getattr(
+        settings, "DIGID_MOCK_IDP_VALIDATE_CALLBACK_URLS", not settings.DEBUG
+    )
     if not isinstance(flag, bool):
         raise ImproperlyConfigured(
             "DIGID_MOCK_IDP_VALIDATE_CALLBACK_URLS should be a boolean"
diff --git a/tests/test_mock_views.py b/tests/test_mock_views.py
index a2fe580..9bf3717 100644
--- a/tests/test_mock_views.py
+++ b/tests/test_mock_views.py
@@ -142,13 +142,13 @@ def test_conf_setting_must_be_a_bool(self):
             should_validate_idp_callback_urls()
 
     @override_settings()
-    def test_conf_setting_defaults_to_debug_flag(self):
+    def test_conf_setting_defaults_to_inverse_of_debug_flag(self):
         del settings.DIGID_MOCK_IDP_VALIDATE_CALLBACK_URLS
 
-        with override_settings(DEBUG=True):
+        with override_settings(DEBUG=False):
             self.assertTrue(should_validate_idp_callback_urls())
 
-        with override_settings(DEBUG=False):
+        with override_settings(DEBUG=True):
             self.assertFalse(should_validate_idp_callback_urls())