Fix handling of new config option

fixes #256
diff --git a/ChangeLog b/ChangeLog
index 2da6a2a..b61c2c5 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,5 +1,11 @@
 mbed TLS ChangeLog (Sorted per branch, date)
 
+= mbed TLS 1.3.13 reladsed 2015-??-??
+
+Bugfix
+   * Setting SSL_MIN_DHM_BYTES in config.h had no effect (overriden in ssl.h)
+     (found by Fabio Solari) (#256)
+
 = mbed TLS 1.3.12 released 2015-08-11
 
 Security