diff --git a/README.asciidoc b/README.asciidoc
index edcd471f..833a4469 100644
--- a/README.asciidoc
+++ b/README.asciidoc
@@ -351,6 +351,7 @@ Movement
 
  * `x`: select line on which selection end lies (or next line when end lies on
         an end-of-line)
+ * `X`: similar to `x`, except the current selection is extended
  * `<a-x>`: expand selections to contain full lines (including end-of-lines)
  * `<a-X>`: trim selections to only contain full lines (not including last
             end-of-line)
diff --git a/doc/manpages/keys.asciidoc b/doc/manpages/keys.asciidoc
index 1290a2b7..63a96844 100644
--- a/doc/manpages/keys.asciidoc
+++ b/doc/manpages/keys.asciidoc
@@ -137,6 +137,8 @@ is a sequence of non whitespace characters
 	select line on which selection end lies (or next line when end lies
 	on an end-of-line)
 
+*X*:: similar to *x*, except the current selection is extended
+
 *<a-x>*::
 	expand selections to contain full lines (including end-of-lines)