# Drivers not working when running blender in the background from command line

I am trying to animate a Blender file from the command line that is using a couple of Python functions for Drivers. However, the command gives the following error, and consequently does not perform the animations.

    $blender -b QCM.blend -y read blend: /home/brent/Downloads/QCM/QCM.blend Error in Driver: The following Python expression failed: 'crystal_driver(frame)' Traceback (most recent call last): File "<bpy driver>", line 1, in <module> NameError: name 'crystal_driver' is not defined Error in Driver: The following Python expression failed: 'film_driver(frame)' Traceback (most recent call last): File "<bpy driver>", line 1, in <module> NameError: name 'film_driver' is not defined  If I run the file without the background switch, the animation works as expected: $blender -y QCM.blend