additionalStreams not working

Given the below code, which I've simplified to make more readable:

``` js
gulp.task('build', function() {
var templateStream = gulp.src('src/**/!(index).html')
.pipe(processTemplates()) // lazypipe that just calls gulp-angular-templatecache.

return gulp.src('src/index.html')
.pipe(addTemplateToIndex()) // Adds reference to 'app/app.templates.js'.
.pipe($.useref({
additionalStreams: [templateStream]
}))
.pipe($.if('app/**/*.js', processOwnJs()))
.pipe($.if('*.js', processAllJs()))
.pipe($.if('*.html', processAllHtml()))
.pipe(gulp.dest('dist'));
});
```

I'm getting a `File not found with singular glob` error, specifying the full absolute path of the 'app/app.templates.js' file.

I can't seem to figure out what exactly is going wrong; through inserting a few calls to gulp-debug I can see that the app.templates.js file appears to be getting passed along with the expected cwd, base and path properties.