diff --git a/examples/problems/parametric_poisson.py b/examples/problems/parametric_poisson.py
index c6581cb..58867d5 100644
--- a/examples/problems/parametric_poisson.py
+++ b/examples/problems/parametric_poisson.py
@@ -33,7 +33,7 @@ class ParametricPoisson(SpatialProblem, ParametricProblem):
         force_term = torch.exp(
                 - 2*(input_.extract(['x']) - input_.extract(['mu1']))**2
                 - 2*(input_.extract(['y']) - input_.extract(['mu2']))**2)
-        return laplacian(output_.extract(['u']), input_) - force_term
+        return laplacian(output_.extract(['u']), input_, d=['x','y']) - force_term
 
     # problem condition statement
     conditions = {
@@ -52,4 +52,4 @@ class ParametricPoisson(SpatialProblem, ParametricProblem):
         'D': Condition(
             location=CartesianDomain({'x': [-1, 1], 'y': [-1, 1], 'mu1': [-1, 1], 'mu2': [-1, 1]}),
             equation=Equation(laplace_equation)),
-    }
\ No newline at end of file
+    }