diff --git a/lib/spack/spack/test/spec_list.py b/lib/spack/spack/test/spec_list.py
index b173ff42b1a..a3bb2d60de9 100644
--- a/lib/spack/spack/test/spec_list.py
+++ b/lib/spack/spack/test/spec_list.py
@@ -219,7 +219,8 @@ def test_spec_list_broadcast(self, mock_packages):
         matrix = {
             "matrix": [["mpileaks"], ["^callpath"]],
             "broadcast": [["%gcc", "%clang"], ["+debug", "~debug"]],
-            "exclude": ["+debug%clang"]}
+            "exclude": ["+debug%clang"],
+        }
         speclist = SpecList("specs", [matrix])
 
         assert len(speclist) == 3