diff --git a/runtime/ftplugin/diff.vim b/runtime/ftplugin/diff.vim
new file mode 100644
index 0000000..3fe1b84
--- /dev/null
+++ b/runtime/ftplugin/diff.vim
@@ -0,0 +1,15 @@
+" Vim filetype plugin file
+" Language:	Diff
+" Maintainer:	Bram Moolenaar <Bram@vim.org>
+" Last Change:	2005 Jul 27
+
+" Only do this when not done yet for this buffer
+if exists("b:did_ftplugin")
+  finish
+endif
+let b:did_ftplugin = 1
+
+let b:undo_ftplugin = "setl modeline<"
+
+" Don't use modelines in a diff, they apply to the diffed file
+setlocal nomodeline