version 0.1.16 fails all the time with indexOf warning

[genechan]

Just install 0.1.16 for the first time.
It fails all time, even tested on a simple empty html 5 document.
There's no use of indexOf anywere.

<title>Document</title>

$ grunt html-validation
Running "html-validation:files" (html-validation) task
Warning: Object # has no method 'indexOf' Use --force to continue.

Aborted due to warnings.

grunt settings in grunt file
"html-validation":{
options:{
reset: true,
stoponerror: false,
},
files:[{
expand:true,
cwd:'files/',
src:[
'foobar.html'
],
dest:'files/'
}]
},