diff --git a/webdriver-spec.html b/webdriver-spec.html
index df0f96ba2..04934b1ee 100644
--- a/webdriver-spec.html
+++ b/webdriver-spec.html
@@ -3698,7 +3698,8 @@ <h3>Get Window Handles</h3>
 <p>The <dfn>Get Window Handles</dfn> <a>command</a>
  returns a list of <a>window handles</a>
  for every open <a>top-level browsing context</a>.
- The order in which the window handles are returned is arbitrary.
+ The window handles must be returned in ascending order, sorted by the 
+ timestamp of the creation of their associated <a>top-level browsing context</a>.
 
 <p>The <a>remote end steps</a> are: