diff --git a/workflow/tests/test_pool_and_psuedoreplicate.py b/workflow/tests/test_pool_and_psuedoreplicate.py
index 7d7fd2c93dd6a55a58261ab2fb17432b405fd19a..ba5fe0f61a6db3c7fba46bf4ed9a2f147eb463ca 100644
--- a/workflow/tests/test_pool_and_psuedoreplicate.py
+++ b/workflow/tests/test_pool_and_psuedoreplicate.py
@@ -63,7 +63,7 @@ def test_check_controls_single(design_experiment_3):
 
 @pytest.mark.unit
 def test_single_rep(design_experiment_2):
-    sys.argv.extend(['--design', 'design_experiment_2'])
+    sys.argv[0](['--design', 'design_experiment_2'])
     single_rep = pool_and_psuedoreplicate.main()