This is style-loader@~0.8.0. My *.styl loader looks like this: { test: /\.styl$/, loader: 'style!css!stylus' }.
The offending lines (specifically the one with module.hot.accept):
if(true) {
// When the styles change, update the <style> tags
module.hot.accept(/*! !../~/css-loader!../~/stylus-loader!./viewer.styl */ 2/*! !../~/css-loader!../~/stylus-loader!./viewer.styl */ 2, function() {
var newContent = __webpack_require__(/*! !../~/css-loader!../~/stylus-loader!./viewer.styl */ 2);
if(typeof newContent === 'string') newContent = [module.id, newContent, ''];
update(newContent);
});
// When the module is disposed, remove the <style> tags
module.hot.dispose(function() { update(); });
}