Update Changelog for fix #559
diff --git a/ChangeLog b/ChangeLog
index bbb9671..272845b 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -12,6 +12,9 @@
enabled unless others were also present. Found by David Fernandez. #428
* Fixed cert_app sample program for debug output and for use when no root
certificates are provided.
+ * Fixed sample application 'programs/pkey/gen_key.c' for builds where the
+ configuration MBEDTLS_PEM_WRITE_C is not defined. Found by inestlerode.
+ #559.
= mbed TLS 2.1.5 branch released 2016-06-28