diff --git a/ChangeLog b/ChangeLog
index 096be45..26c7cd3 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -22,8 +22,8 @@
      Inserted as an enhancement for #1371
    * Add support for alternative CSR headers, as used by Microsoft and defined
      in RFC 7468. Found by Michael Ernst. Fixes #767.
-   * Reduced the complexity of the timing tests, as they were failing in less
-     reliable environments.
+   * Reduced the complexity of the timing tests, as they were assuming more than
+     the underlying OS actually guarantees.
 
 = mbed TLS 2.16.0 branch released 2018-12-21