diff --git a/connexion/operation.py b/connexion/operation.py
index cc39c96..ec37a28 100644
--- a/connexion/operation.py
+++ b/connexion/operation.py
@@ -343,7 +343,7 @@ class Operation(SecureOperation):
         logger.debug('... Adding security decorator (%r)', security_decorator, extra=vars(self))
         function = security_decorator(function)
 
-        if UWSGIMetricsCollector.is_available():
+        if UWSGIMetricsCollector.is_available():  # pragma: no cover
             decorator = UWSGIMetricsCollector(self.path, self.method)
             function = decorator(function)
 
diff --git a/tests/api/test_errors.py b/tests/api/test_errors.py
index bb6e31a..6194683 100644
--- a/tests/api/test_errors.py
+++ b/tests/api/test_errors.py
@@ -60,3 +60,9 @@ def test_errors(problem_app):
     problematic_json = app_client.get(
         '/v1.0/json_response_with_undefined_value_to_serialize')  # type: flask.Response
     assert problematic_json.status_code == 500
+
+    custom_problem = app_client.get('/v1.0/customized_problem_response')
+    assert custom_problem.status_code == 402
+    problem_body = json.loads(custom_problem.data.decode('utf-8'))
+    assert 'amount' in problem_body
+    assert problem_body['amount'] == 23.
diff --git a/tests/fakeapi/hello.py b/tests/fakeapi/hello.py
index 73a9b65..9710e26 100755
--- a/tests/fakeapi/hello.py
+++ b/tests/fakeapi/hello.py
@@ -332,3 +332,8 @@ def get_data_as_binary():
 
 def get_invalid_response():
     return {"simple": object()}
+
+
+def get_custom_problem_response():
+    return problem(402, "You need to pay", "Missing amount",
+                   ext={'amount': 23.0})
diff --git a/tests/fixtures/problem/swagger.yaml b/tests/fixtures/problem/swagger.yaml
index 270ce10..4e9836f 100644
--- a/tests/fixtures/problem/swagger.yaml
+++ b/tests/fixtures/problem/swagger.yaml
@@ -81,3 +81,13 @@ paths:
       responses:
         200:
           description: Never happens
+
+  /customized_problem_response:
+    get:
+      description: Custom problem response
+      operationId: fakeapi.hello.get_custom_problem_response
+      produces:
+        - application/json
+      responses:
+        200:
+          description: Custom problem response