Fix wrong context in customImporters

index.js

@@ -18,6 +18,7 @@ var SassError = {
 };
 
 // libsass uses this precedence when importing files without extension
+var slice = Array.prototype.slice;
 var extPrecedence = ['.scss', '.sass', '.css'];
 var matchCss = /\.css$/;
 
@@ -409,7 +410,13 @@ function getLoaderConfig(loaderContext) {
 function proxyCustomImporters(importer, resourcePath) {
     return [].concat(importer).map(function (importer) {
         return function (url, prev, done) {
-            return importer(url, prev === 'stdin' ? resourcePath : prev, done);
+            var args = slice.call(arguments);
+
+            if (args[1] === 'stdin') {
+                args[1] = resourcePath;
+            }
+
+            return importer.apply(this, args);
         };
     });
 }

test/tools/customImporter.js

@@ -3,8 +3,13 @@
 var should = require('should');
 
 function customImporter(path, prev) {
+    /*jshint validthis: true */
+
     path.should.equal('import-with-custom-logic');
     prev.should.match(/(sass|scss)[/\\]custom-importer\.(scss|sass)/);
+
+    this.should.have.property('options');
+
     return customImporter.returnValue;
 }
 customImporter.returnValue = {