diff --git a/runtime/ftplugin/sexplib.vim b/runtime/ftplugin/sexplib.vim
new file mode 100644
index 0000000..27e1b28
--- /dev/null
+++ b/runtime/ftplugin/sexplib.vim
@@ -0,0 +1,15 @@
+" Vim filetype plugin file
+" Language:    Sexplib
+" Maintainer:  Markus Mottl        <markus.mottl@gmail.com>
+" URL:         https://github.com/ocaml/vim-ocaml
+" Last Change:
+"              2017 Apr 12 - First version (MM)
+
+if exists("b:did_ftplugin")
+  finish
+endif
+let b:did_ftplugin=1
+
+" Comment string
+setl commentstring=;\ %s
+setl comments=:;