diff --git a/annotations.md b/annotations.md
index 8abbf9b8..c0f12f32 100644
--- a/annotations.md
+++ b/annotations.md
@@ -33,7 +33,7 @@ This specification defines the following annotation keys, intended for but not l
 - **org.opencontainers.image.ref.name** Name of the reference for a target (string).
   - SHOULD only be considered valid when on descriptors on `index.json` within [image layout](image-layout.md).
   - Character set of the value SHOULD conform to alphanum of `A-Za-z0-9` and separator set of `-._:@/+`
-  - The reference must match the following [grammar](considerations.md#ebnf):
+  - The reference MUST match the following [grammar](considerations.md#ebnf):
 
     ```ebnf
     ref       ::= component ("/" component)*