Compile Flex 4 theme in Flash Builder 4

How to compile Flex theme SWC from file.css and additional skin classes in Flash Builder 4?

I've tried creating simple Fle开发者_JS百科x Library project but it does not seem to use CSS file because resulting SWC does not work as theme.

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It has started working after adding defaults.css to the library assets and mx|Button class declaration. Seems like a bug for me.