diff --git a/source/multiple-mongosyncs.txt b/source/multiple-mongosyncs.txt
index 8c2f078a3..9a586ec98 100644
--- a/source/multiple-mongosyncs.txt
+++ b/source/multiple-mongosyncs.txt
@@ -40,7 +40,8 @@ Configure Multiple ``mongosync`` Instances
 ------------------------------------------
 
 The number of ``mongosync`` instances must match the number of shards on
-the source cluster. For a replica set source, you can only use one
+the source cluster. You must use the same version of ``mongosync``
+between all instances. For a replica set source, you can only use one
 ``mongosync`` instance. 
 
 To configure multiple ``mongosync`` instances: