Recursion gives stack overflow

The following code gives me stack overflow. Any idea why? Thanks.

~~~
local lustache = require'lustache'

local tree = [[
{{#files}}
	{{path}}
	{{>tree}}
{{/files}}
]]

local root = {
	path = '',
	files = {
		path = 'files',
		files = false,
	}
}

print(lustache:render(tree, root, {tree = tree}))
~~~
