diff --git a/source/includes/fact-upgrade-sharded-cluster-prereq.rst b/source/includes/fact-upgrade-sharded-cluster-prereq.rst
index c7315883913..f4655ac357d 100644
--- a/source/includes/fact-upgrade-sharded-cluster-prereq.rst
+++ b/source/includes/fact-upgrade-sharded-cluster-prereq.rst
@@ -6,6 +6,6 @@ currently used by the :doc:`config database
 
 Additionally, ensure that all indexes in the :doc:`config database
 </reference/config-database>` are ``{v:1}`` indexes. If a critical
-index is a ``{v:0}`` index, chunk splits can fail following the
-upgrade. ``{v:0}`` indexes are present on clusters created with
+index is a ``{v:0}`` index, chunk splits can fail due to known issues
+with the ``{v:0}`` format. ``{v:0}`` indexes are present on clusters created with
 MongoDB 2.0 or earlier.