Adds referene in ChangeLog for issue #1623
diff --git a/ChangeLog b/ChangeLog
index 84d4cee..24d2050 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -4,7 +4,7 @@
 
 Bugfix
    * Fix a memory leak in mbedtls_x509_csr_parse(), found by catenacyber,
-     Philippe Antoine.
+     Philippe Antoine. Fixes #1623.
    * Clarify documentation for mbedtls_ssl_write() to include 0 as a valid
      return value. Found by @davidwu2000. #839
    * Fix the key_app_writer example which was writing a leading zero byte which