lisp-source-modes

lisp-source-modes is a variable defined in `inf-lisp.el'.
Its value is

(lisp-mode)

Documentation:
Used to determine if a buffer contains Lisp source code.
If it's loaded into a buffer that is in one of these major modes, it's
considered a Lisp source file by `lisp-load-file' and `lisp-compile-file'.
Used by these commands to determine defaults.

You can customize this variable.