BASIC looks for foo.bas.d, which is not a valid filename under CP/M

The BASIC compiler stores data in a file based on the source filename with ".d" appended.
For a file like "foo.bas" it uses "foo.bas.d". However, this is not a valid filename on the CP/M platform.
Could you use "foo.d" instead?
Some of the source code comments (in lang/basic/src/initialize.c) imply that the .bas was supposed to be stripped from the filename?