diff --git a/lib/spack/spack/test/spec_list.py b/lib/spack/spack/test/spec_list.py
index b877c095ce2..b173ff42b1a 100644
--- a/lib/spack/spack/test/spec_list.py
+++ b/lib/spack/spack/test/spec_list.py
@@ -219,10 +219,10 @@ def test_spec_list_broadcast(self, mock_packages):
         matrix = {
             "matrix": [["mpileaks"], ["^callpath"]],
             "broadcast": [["%gcc", "%clang"], ["+debug", "~debug"]],
-        }
+            "exclude": ["+debug%clang"]}
         speclist = SpecList("specs", [matrix])
 
-        assert len(speclist) == 4
+        assert len(speclist) == 3
         for spec in speclist:
             for node in spec.traverse():
                 assert node.compiler.name == spec.compiler.name