IE Developer Tools breakpoints are not working

I'm trying to debug some javascript in IE 11 and I'm not able to force it to stop on a breakpoint.

debugger; line works fine (stops debugger in that line), same file without a debugger; line but with a breakpoint set in the same place does nothing (function works fine, but debugger does not stop on a breakpoint).

Chrome's and Firefox's debuggers stop on breakpoints in the same places.

Any thoughts what could be the cause of this behavior?