diff --git a/RELEASE_NOTES.rst b/RELEASE_NOTES.rst
index 467e4e9c4..54cb3a284 100644
--- a/RELEASE_NOTES.rst
+++ b/RELEASE_NOTES.rst
@@ -38,6 +38,7 @@ Breaking changes:
 * Phaser: fixed coarse mixer frequency configuration
 * Mirny: Added extra delays in ``ADF5356.sync()``. This avoids the need of an extra delay before
   calling `ADF5356.init()`.
+* DRTIO: Changed message alignment from 32-bits to 64-bits.
 
 
 ARTIQ-6