diff --git a/src/pymor/operators/numpy.py b/src/pymor/operators/numpy.py
index bdb53eb4..7ea83f35 100644
--- a/src/pymor/operators/numpy.py
+++ b/src/pymor/operators/numpy.py
@@ -96,6 +96,12 @@ class NumpyGenericOperator(OperatorBase):
         else:
             return self.source.make_array(self._adjoint_mapping(V))
 
+    def jacobian(self, U, mu=None):
+        raise NotImplementedError
+
+    def assemble(self, mu=None):
+        raise NotImplementedError
+
 
 class NumpyMatrixBasedOperator(OperatorBase):
     """Base class for operators which assemble into a |NumpyMatrixOperator|.