diff --git a/runtime/pack/dist/opt/nvim.undotree/lua/undotree.lua b/runtime/pack/dist/opt/nvim.undotree/lua/undotree.lua
index 3edae8d4e4..14875fa464 100644
--- a/runtime/pack/dist/opt/nvim.undotree/lua/undotree.lua
+++ b/runtime/pack/dist/opt/nvim.undotree/lua/undotree.lua
@@ -401,6 +401,8 @@ function M.open(opts)
       end
     end,
   })
+
+  vim.bo[b].filetype = 'nvim-undotree'
 end
 
 return M