JSHint considers a for-in variable 'bad'. What does this mean?-open source projects jshint/jshint

The following code:

var things = {'foo':'bar'}
for ( thing in things ) {

Consistently produces the following error in jshint:

Bad for in variable 'thing'.

I do not understand what makes the ‘thing’ variable ‘bad’ – as you can see, it is not being used anywhere else. What should I do differently to make jshint not consider this to be an error?