In a system such as (defsystem :foo :component ((:file "foo"))) where foo.lsp exists and is recognized by the lisp implementation as a valid source file (ECL), ASDF imposes the file extension "lisp". Furthermore, adding our own extension (defsystem :foo :component ((:file "foo.lsp"))) does not work and one has to resort to an EQL-specialized method (ugly!) I have submitted a small patch that adds a new option :type that can be used with components of the type source-file https://bugs.launchpad.net/asdf/+bug/542222 -- Instituto de Física Fundamental, CSIC c/ Serrano, 113b, Madrid 28006 (Spain) http://tream.dreamhosters.com