diff --git a/flask_restx/api.py b/flask_restx/api.py
index 0e561f86..dd4d318d 100644
--- a/flask_restx/api.py
+++ b/flask_restx/api.py
@@ -666,7 +666,7 @@ def handle_error(self, e):
         if (
             not isinstance(e, HTTPException)
             and current_app.propagate_exceptions
-            and not isinstance(e, tuple(self.error_handlers.keys()))
+            and not isinstance(e, tuple(self._own_and_child_error_handlers.keys()))
         ):
 
             exc_type, exc_value, tb = sys.exc_info()
diff --git a/tests/test_errors.py b/tests/test_errors.py
index 10fdc2ea..e1ce03ff 100644
--- a/tests/test_errors.py
+++ b/tests/test_errors.py
@@ -653,3 +653,30 @@ def handle_custom_exception(error):
             "message": "error",
             "test": "value",
         }
+
+    def test_namespace_errorhandler_with_propagate_true(self, app, client):
+        """Exceptions with errorhandler on a namespace should not be
+        returned to client, even if PROPAGATE_EXCEPTIONS is set."""
+        app.config["PROPAGATE_EXCEPTIONS"] = True
+        api = restx.Api(app)
+        namespace = restx.Namespace('test_namespace')
+        api.add_namespace(namespace)
+
+        @namespace.route("/test/", endpoint="test")
+        class TestResource(restx.Resource):
+            def get(self):
+                raise RuntimeError("error")
+
+        @namespace.errorhandler(RuntimeError)
+        def handle_custom_exception(error):
+            return {"message": str(error), "test": "value"}, 400
+
+        response = client.get("/test_namespace/test/")
+        assert response.status_code == 400
+        assert response.content_type == "application/json"
+
+        data = json.loads(response.data.decode("utf8"))
+        assert data == {
+            "message": "error",
+            "test": "value",
+        }