diff --git a/hog/forms.py b/hog/forms.py
index 774752bb4c99066c8a46b8157c2bb01c7bc11209..e8dc31b1c7c1926cfa900479aa5f3b0d52111645 100644
--- a/hog/forms.py
+++ b/hog/forms.py
@@ -375,7 +375,7 @@ def k_mass(
     coefficient_function_space: Optional[FunctionSpace] = None,
 ) -> Form:
     docstring = f"""
-Diffusion operator with a scalar coefficient.
+Mass operator scaled with a coefficient.
 
 Geometry map: {blending}
 
@@ -398,6 +398,7 @@ Weak formulation
         symbolizer,
         blending=blending,
         is_symmetric=trial == test,
+        fe_coefficients={"k": coefficient_function_space},
         docstring=docstring,
     )