diff --git a/spec/intro.md b/spec/intro.md
index 433f0e3ee5..babe88cca8 100644
--- a/spec/intro.md
+++ b/spec/intro.md
@@ -78,7 +78,7 @@ A reference to a _term_ looks like this.
 
 ### Stability Policy
 
-Updates to this specification will not make any valid _message_ invalid.
+Updates to this specification will not make any _valid_ _message_ become not _valid_.
 
 Updates to this specification will not specify an _error_ for any _message_
 that previously did not specify an _error_.