diff --git a/ChangeLog.d/semi-public-structure-fields.txt b/ChangeLog.d/semi-public-structure-fields.txt
new file mode 100644
index 000000000..802f8de2b
--- /dev/null
+++ b/ChangeLog.d/semi-public-structure-fields.txt
@@ -0,0 +1,5 @@
+API changes
+   * Some fields of mbedtls_ssl_session and mbedtls_ssl_config are in a
+     different order. This only affects applications that define such
+     structures directly or serialize them.
+