diff --git a/docker/Dockerfile.firedrake b/docker/Dockerfile.firedrake
index cd5252eb989352c820e8abe822d28f6861d3d20a..c8c83a83cbb2444c2a1d4b0cac37de80b6a276a7 100644
--- a/docker/Dockerfile.firedrake
+++ b/docker/Dockerfile.firedrake
@@ -30,3 +30,5 @@ RUN bash -c "source ~/firedrake/bin/activate; cd volumential/contrib/meshgen11_d
 RUN bash -c "source ~/firedrake/bin/activate; cd volumential; pip install -r requirements.txt"
 COPY docker/to_loopyy.sh .
 RUN bash -c "source ~/firedrake/bin/activate; sh to_loopyy.sh"
+
+WORKDIR /home/firedrake/
diff --git a/test/test_interpolation.py b/test/test_interpolation.py
index 9135c2109d0c48c392f2fb7a503912094bf2cae1..8d2ae6ca533ba28a6a97f2334afafb28d5cb38fa 100644
--- a/test/test_interpolation.py
+++ b/test/test_interpolation.py
@@ -51,9 +51,11 @@ def random_polynomial_func(dim, degree, seed=None):
         npts = pts.shape[1]
         res = np.zeros(npts)
         for deg in np.ndindex(coefs.shape):
+            if sum(deg) > degree:
+                continue
             mono = np.ones(npts)
             for iaxis in range(dim):
-                mono += pts[iaxis, :]**deg[iaxis]
+                mono *= pts[iaxis, :]**deg[iaxis]
             res += coefs[deg] * mono
         return res