Is the little thing that prevents the shoelace from “untying” broken (pic 2)? Just print this thing to keep that sucker from “untying” itself! 

NOTE the hole may be undersized/oversized, so you can scale it or use some tape to make the shoelace bigger, like I did

NOTE2 the version in the pic is an older, slightly bigger, version. I haven't printed the file, but it should still work ;)