diff --git a/activesupport/lib/active_support/testing/assertions.rb b/activesupport/lib/active_support/testing/assertions.rb
index <HASH>..<HASH> 100644
--- a/activesupport/lib/active_support/testing/assertions.rb
+++ b/activesupport/lib/active_support/testing/assertions.rb
@@ -167,7 +167,7 @@ module ActiveSupport
         retval
       end
 
-      # Assertion that the result of evaluating an expression is changed before
+      # Assertion that the result of evaluating an expression is not changed before
       # and after invoking the passed in block.
       #
       #   assert_no_changes 'Status.all_good?' do
Add missing "not" in the doc for `assert_no_changes` [ci skip]