Templates with liquid extension cause error

[kslstn]

My templates have the .liquid extension, so my editor can apply the appropriate syntax highlighting. The data page generator doesn't seem to like that:

Error reading file /[project path]/_layouts/test.liquid/test.liquid: Not a directory @ rb_sysopen - /[project path]/_layouts/test.liquid/test.liquid 

When I change the file extension to .html, there's no error and the pages are rendered.