diff --git a/runtime/doc/vimdiff.1 b/runtime/doc/vimdiff.1
index 90ed8b8..bed2b32 100644
--- a/runtime/doc/vimdiff.1
+++ b/runtime/doc/vimdiff.1
@@ -1,17 +1,17 @@
 .TH VIMDIFF 1 "2001 March 30"
 .SH NAME
-vimdiff \- edit two or three versions of a file with Vim and show differences
+vimdiff \- edit two, three or four versions of a file with Vim and show differences
 .SH SYNOPSIS
 .br
 .B vimdiff
-[options] file1 file2 [file3]
+[options] file1 file2 [file3 [file4]]
 .PP
 .B gvimdiff
 .SH DESCRIPTION
 .B Vimdiff
 starts
 .B Vim
-on two (or three) files.
+on two (or three or four) files.
 Each file gets its own window.
 The differences between the files are highlighted.
 This is a nice way to inspect changes and to move changes from one version