diff --git a/ChangeLog b/ChangeLog
index e8fa013..32f930b 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -3,6 +3,8 @@
 = mbed TLS 2.1.x branch released xxxx-xx-xx
 
 Bugfix
+   * Fix redefinition of macro ssl_set_bio to undefined symbol
+     mbedtls_ssl_set_bio_timeout in compat-1.3.h. #673
    * Fixed multiple buffer overreads in mbedtls_pem_read_buffer() when parsing
      the input string in PEM format to extract the different components. Found
      by Eyal Itkin.