diff --git a/ChangeLog b/ChangeLog
index bda3de8..d8b2829 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -5,6 +5,8 @@
 Bugfix
    * Fixes an issue with MBEDTLS_CHACHAPOLY_C which would not compile if
      MBEDTLS_ARC4_C and MBEDTLS_CIPHER_NULL_CIPHER weren't also defined. #1890
+   * Fix build failures on where only gmtime() is available but neither
+     gmtime_r() nor gmtime_s() are present. Fixes #1907.
 
 = mbed TLS 2.12.0 branch released 2018-07-25