diff --git a/runtime/doc/builtin.txt b/runtime/doc/builtin.txt
index 2dc8f61..f1256b0 100644
--- a/runtime/doc/builtin.txt
+++ b/runtime/doc/builtin.txt
@@ -2540,6 +2540,9 @@
 		for a non-existing file is not included, unless {string} does
 		not start with '%', '#' or '<', see below.
 
+		For a |:terminal| window '%' expands to a '!' followed by
+		the command or shell that is run |terminal-bufname|
+
 		When {string} starts with '%', '#' or '<', the expansion is
 		done like for the |cmdline-special| variables with their
 		associated modifiers.  Here is a short overview: