Istanbul cover tests hang, then abort after 60 seconds

I'm using Istanbul for code coverage for a web app I'm creating. Whenever I run "npm run cover --color=always" (which runs

../node_modules/babel-cli/bin/babel-node.js -- node_modules/.bin/babel- istanbul cover test/index.js --report=cobertura --print=detail --x=dist/**

), but nothing appears on the terminal until around 60 seconds later, when I get this error:

TAP version 13
# application server
Aborted (core dumped)

However, if I write something that causes an error (like an undefined function) at the bottom of the index.js file, it will print the coverage out, along with that error.

Any thoughts on what could be wrong?