diff --git a/src/sage/rings/localization.py b/src/sage/rings/localization.py
index 794524a6d4a..5f9e506bdff 100644
--- a/src/sage/rings/localization.py
+++ b/src/sage/rings/localization.py
@@ -369,7 +369,7 @@ def factor(self, proof=None):
 
         INPUT:
 
-        - ``proof`` -- optional if given it is passed to the
+        - ``proof`` -- (optional) if given it is passed to the
           corresponding method of the numerator of ``self``
 
         EXAMPLES::