diff --git a/tensorflow_probability/python/internal/backend/numpy/gen/linear_operator.py b/tensorflow_probability/python/internal/backend/numpy/gen/linear_operator.py
index a7af244ec3..e8c7f52fb3 100644
--- a/tensorflow_probability/python/internal/backend/numpy/gen/linear_operator.py
+++ b/tensorflow_probability/python/internal/backend/numpy/gen/linear_operator.py
@@ -1675,7 +1675,10 @@ def _matmul(  # pylint:disable=missing-docstring
     a_is_sparse=False,
     b_is_sparse=False,
     output_type=None,  # pylint: disable=unused-argument
-    name=None):
+    grad_a=False,  # pylint: disable=unused-argument
+    grad_b=False,  # pylint: disable=unused-argument
+    name=None,
+):
   if transpose_a or transpose_b:
     raise ValueError("Transposing not supported at this time.")
   if a_is_sparse or b_is_sparse: