diff --git a/tests/dirac_test.py b/tests/dirac_test.py
index 719490f4..0a2c0379 100644
--- a/tests/dirac_test.py
+++ b/tests/dirac_test.py
@@ -30,3 +30,5 @@ def test_grid_dirac():
                   'SigmaYZ',
                   'SigmaZT']:
         pe.dirac.Grid_gamma(gamma)
+    with pytest.raises(Exception):
+        pe.dirac.Grid_gamma('Not a gamma matrix')