Can't include other custom scripts in gsc script

[bradstv]

When trying to include other custom scripts in my gsc script using #include, I get the following error:
main.gsc

#include custom_scripts\test;
init()
{
    print("Print from main.gsc");
    test_print();
}

test.gsc

test_print()
{
    print("Print from test.gsc");
}

Output

*********** script compile error *************
failed to compile 'custom_scripts/main':
[ERROR]: parsing include file 'custom_scripts/test': Could not load gsc file 'custom_scripts/test'
**********************************************

However, calling functions from other custom scripts like this seems to work just fine:

init()
{
    print("Print from main.gsc");
    custom_scripts\test::test_print();
}

Output

Print from main.gsc
Print from test.gsc

I can also include stock scripts just fine, so this seems to only be related to custom scripts.