Added ChangeLog entry
diff --git a/ChangeLog b/ChangeLog
index 90c6e6b..159f4cb 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -24,6 +24,7 @@
      encoded X509 CSRs. The overflow would enable maliciously constructed CSRs
      to bypass the version verification check. Found by Peng Li/Yueh-Hsun Lin,
      KNOX Security, Samsung Research America
+   * Fix word size check in in pk.c to not depend on MBEDTLS_HAVE_INT64.
 
 = mbed TLS 1.3.20 branch released 2017-06-21