diff --git a/site-modules/core/files/vim/plugin/fmt.vim b/site-modules/core/files/vim/plugin/fmt.vim
index fd5c87b..583035f 100644
--- a/site-modules/core/files/vim/plugin/fmt.vim
+++ b/site-modules/core/files/vim/plugin/fmt.vim
@@ -2,10 +2,18 @@
 " Functions to toggle format on save with Neoformat. This is off by default so
 " I don't accidentally start formatting when rebasing (bad memories).
 
+function s:format_on_save()
+  if &filetype == 'fsharp'
+    return execute('lua vim.lsp.buf.format()')
+  endif
+
+  undojoin | Neoformat
+endfunction
+
 function s:fmt_on_save_enable()
   augroup aa_fmt
     autocmd!
-    autocmd BufWritePre * undojoin | Neoformat
+    autocmd BufWritePre * call s:format_on_save()
   augroup END
 endfunction