diff --git a/ChangeLog.d/509write_crt_set_serial_raw-alignment.txt b/ChangeLog.d/509write_crt_set_serial_raw-alignment.txt
new file mode 100644
index 0000000000..1fc938bdcb
--- /dev/null
+++ b/ChangeLog.d/509write_crt_set_serial_raw-alignment.txt
@@ -0,0 +1,3 @@
+API changes
+    * Change the serial argument of the mbedtls_x509write_crt_set_serial_raw
+      function so a const to align with the restof the API.