diff --git a/RELEASE-NOTES b/RELEASE-NOTES
index 713f64dce1..cf3b5e7ab1 100644
--- a/RELEASE-NOTES
+++ b/RELEASE-NOTES
@@ -92,6 +92,8 @@ The following new LyX functions have been introduced:
 
 - LFUN_INSET_COPY_AS ("inset-copy-as").
 
+- LFUN_BUFFER_TOGGLE_OUTPUT_SYNC ("buffer-toggle-output-sync")
+
 
 The following LyX functions have been removed: