diff --git a/openfisca_core/commons/tests/test_rates.py b/openfisca_core/commons/tests/test_rates.py
index ce3781a258..760a188bdc 100644
--- a/openfisca_core/commons/tests/test_rates.py
+++ b/openfisca_core/commons/tests/test_rates.py
@@ -18,7 +18,7 @@ def test_average_rate_when_varying_is_zero():
 
 
 def test_marginal_rate_when_varying_is_zero():
-    """When the varying gross income crosses zero it yields infinity."""
+    """Yields infinity when the varying gross income crosses zero."""
 
     target = numpy.array([1, 2, 3])
     varying = numpy.array([0, 0])