diff --git a/syndicate/mc/preserve.md b/syndicate/mc/preserve.md
index 858005f..fd4bd4c 100644
--- a/syndicate/mc/preserve.md
+++ b/syndicate/mc/preserve.md
@@ -647,7 +647,7 @@ order.
     the option of serializing with set elements and dictionary keys in
     sorted order.
 
-Note that `header(3,3,m)` and `open(3,3)`/`close(3,3)` is unused and reserved.
+Note that `header(3,3,m)` and `open(3,3)`/`close(3,3)` are unused and reserved.
 
 ### SignedIntegers