Coder not finding errors in include files

I have three code files that coder scans:
mymodule.module
mymodule.php
mymodule_func.inc.php

It finds errors in mymodule.module, but not the other two files. I know for sure it should pick something up.
For example, this line in mymodule.php should trigger the error that there are no curly braces around the table name:
$uq = db_query("SELECT * FROM sessions WHERE sid = '%s'", $sessid);