diff --git a/runtime/doc/options.txt b/runtime/doc/options.txt
index 5df5f30..08bc78d 100644
--- a/runtime/doc/options.txt
+++ b/runtime/doc/options.txt
@@ -2634,6 +2634,9 @@
 		vertical	Start diff mode with vertical splits (unless
 				explicitly specified otherwise).
 
+		hiddenoff	Do not use diff mode for a buffer when it
+				becomes hidden.
+
 		foldcolumn:{n}	Set the 'foldcolumn' option to {n} when
 				starting diff mode.  Without this 2 is used.