diff --git a/runtime/indent/dune.vim b/runtime/indent/dune.vim
new file mode 100644
index 0000000..0590d66
--- /dev/null
+++ b/runtime/indent/dune.vim
@@ -0,0 +1,13 @@
+" Vim indent file
+" Language: dune
+" Maintainers:  Markus Mottl         <markus.mottl@gmail.com>
+" URL:          https://github.com/ocaml/vim-ocaml
+" Last Change:  2021 Jan 01
+
+if exists("b:did_indent")
+ finish
+endif
+let b:did_indent = 1
+
+" dune format-dune-file uses 1 space to indent
+setlocal softtabstop=1 shiftwidth=1 expandtab