diff --git a/.editorconfig b/.editorconfig
new file mode 100644
index 0000000..c330fbd
--- /dev/null
+++ b/.editorconfig
@@ -0,0 +1,2 @@
+[*.js]
+indent_style = tab
diff --git a/index.js b/index.js
index 6137235..df899fb 100644
--- a/index.js
+++ b/index.js
@@ -4,8 +4,8 @@
 */
 var fs = require("fs");
 var path = require("path");
-var async = require("async");
 var loaderUtils = require("loader-utils");
+var urlUtils = require("url");
 
 // Matches only the last occurrence of sourceMappingURL
 var baseRegex = "\\s*[@#]\\s*sourceMappingURL\\s*=\\s*([^\\s]*)(?![\\S\\s]*sourceMappingURL)",
@@ -14,98 +14,129 @@ var baseRegex = "\\s*[@#]\\s*sourceMappingURL\\s*=\\s*([^\\s]*)(?![\\S\\s]*sourc
 	// Matches // .... comments
 	regex2 = new RegExp("//"+baseRegex+"($|\n|\r\n?)"),
 	// Matches DataUrls
-	regexDataUrl = /data:[^;\n]+(?:;charset=[^;\n]+)?;base64,([a-zA-Z0-9+/]+={0,2})/;
+	regexDataUrl = /data:[^;\n]+(?:;charset=[^;\n]+)?;base64,([a-zA-Z0-9+/]+={0,2})/,
+	// Matches url with scheme, doesn't match Windows disk
+	regexUrl = /[a-zA-Z]{2,}:/;
+
+const FILE_SCHEME = "file:";
+
+const DEFAULT_OPTIONS = {
+	// Prevent the loader to rewrite all sources as absolute paths
+	keepRelativeSources: false
+};
 
 module.exports = function(input, inputMap) {
+	const options = Object.assign({}, DEFAULT_OPTIONS, loaderUtils.getOptions(this));
 	this.cacheable && this.cacheable();
-	var resolve = this.resolve;
 	var addDependency = this.addDependency;
 	var emitWarning = this.emitWarning || function() {};
 	var match = input.match(regex1) || input.match(regex2);
+	var callback;
 	if(match) {
 		var url = match[1];
 		var dataUrlMatch = regexDataUrl.exec(url);
-		var callback = this.async();
+		callback = this.async();
 		if(dataUrlMatch) {
 			var mapBase64 = dataUrlMatch[1];
-			var mapStr = (new Buffer(mapBase64, "base64")).toString();
+			var mapStr = Buffer.from(mapBase64, "base64").toString();
 			var map;
 			try {
 				map = JSON.parse(mapStr)
 			} catch (e) {
-				emitWarning("Cannot parse inline SourceMap '" + mapBase64.substr(0, 50) + "': " + e);
+				emitWarning(new Error("Cannot parse inline SourceMap '"
+					+ mapBase64.substr(0, 50) + "': " + e));
 				return untouched();
 			}
 			processMap(map, this.context, callback);
 		} else {
-			resolve(this.context, loaderUtils.urlToRequest(url, true), function(err, result) {
+			resolveAbsolutePath(this.context, url, function(err, absoluteFilepath) {
 				if(err) {
-					emitWarning("Cannot find SourceMap '" + url + "': " + err);
+					emitWarning(new Error("Cannot find SourceMap '" + url + "': " + err));
 					return untouched();
 				}
-				addDependency(result);
-				fs.readFile(result, "utf-8", function(err, content) {
+				fs.readFile(absoluteFilepath, "utf-8", function(err, content) {
 					if(err) {
-						emitWarning("Cannot open SourceMap '" + result + "': " + err);
+						emitWarning(new Error("Cannot open SourceMap '" + absoluteFilepath + "': " + err));
 						return untouched();
 					}
+					addDependency(absoluteFilepath);
 					var map;
 					try {
 						map = JSON.parse(content);
 					} catch (e) {
-						emitWarning("Cannot parse SourceMap '" + url + "': " + e);
+						emitWarning(new Error("Cannot parse SourceMap '" + url + "': " + e));
 						return untouched();
 					}
-					processMap(map, path.dirname(result), callback);
+					processMap(map, path.dirname(absoluteFilepath), callback);
 				});
 			}.bind(this));
-			return;
 		}
 	} else {
-		var callback = this.callback;
+		callback = this.callback;
 		return untouched();
 	}
 	function untouched() {
 		callback(null, input, inputMap);
 	}
+	function resolveAbsolutePath(context, url, resolveAbsolutePathCallback) {
+		let filepath = url;
+		if(regexUrl.test(filepath) && !filepath.startsWith(FILE_SCHEME)) {
+			resolveAbsolutePathCallback("URL scheme not supported");
+			return;
+		}
+		if(filepath.startsWith(FILE_SCHEME)) {
+			if(urlUtils.fileURLToPath) {
+				filepath = urlUtils.fileURLToPath(filepath);
+			} else {
+				resolveAbsolutePathCallback("file URL scheme support requires node 10.x");
+				return;
+			}
+		}
+		resolveAbsolutePathCallback(null, path.resolve(context, filepath));
+	}
 	function processMap(map, context, callback) {
-		if(!map.sourcesContent || map.sourcesContent.length < map.sources.length) {
-			var sourcePrefix = map.sourceRoot ? map.sourceRoot + "/" : "";
-			map.sources = map.sources.map(function(s) { return sourcePrefix + s; });
-			delete map.sourceRoot;
-			var missingSources = map.sourcesContent ? map.sources.slice(map.sourcesContent.length) : map.sources;
-			async.map(missingSources, function(source, callback) {
-				resolve(context, loaderUtils.urlToRequest(source, true), function(err, result) {
+		const sourcePrefix = map.sourceRoot ? map.sourceRoot + "/" : "";
+		const sources = map.sources.map(function(s) { return sourcePrefix + s; });
+		delete map.sourceRoot;
+		const sourcesContent = map.sourcesContent || [];
+		const sourcesPromises = sources.map((source, sourceIndex) => new Promise((resolveSource) => {
+			resolveAbsolutePath(context, source, function(err, absoluteFilepath) {
+				if(err) {
+					emitWarning(new Error("Cannot find source file '" + source + "': " + err));
+					return resolveSource({
+						source: source,
+						content: sourcesContent[sourceIndex] != null ? sourcesContent[sourceIndex] : null
+					});
+				}
+				if(sourcesContent[sourceIndex] != null) {
+					return resolveSource({
+						source: absoluteFilepath,
+						content: sourcesContent[sourceIndex]
+					});
+				}
+				fs.readFile(absoluteFilepath, "utf-8", function(err, content) {
 					if(err) {
-						emitWarning("Cannot find source file '" + source + "': " + err);
-						return callback(null, null);
-					}
-					addDependency(result);
-					fs.readFile(result, "utf-8", function(err, content) {
-						if(err) {
-							emitWarning("Cannot open source file '" + result + "': " + err);
-							return callback(null, null);
-						}
-						callback(null, {
-							source: result,
-							content: content
+						emitWarning(new Error("Cannot open source file '" + absoluteFilepath + "': " + err));
+						return resolveSource({
+							source: absoluteFilepath,
+							content: null
 						});
-					});
-				});
-			}, function(err, info) {
-				map.sourcesContent = map.sourcesContent || [];
-				info.forEach(function(res) {
-					if(res) {
-						map.sources[map.sourcesContent.length] = res.source;
-						map.sourcesContent.push(res.content);
-					} else {
-						map.sourcesContent.push(null);
 					}
+					addDependency(absoluteFilepath);
+					resolveSource({
+						source: absoluteFilepath,
+						content: content
+					});
 				});
-				processMap(map, context, callback);
 			});
-			return;
-		}
-		callback(null, input.replace(match[0], ''), map);
+		}));
+		Promise.all(sourcesPromises)
+			.then((results) => {
+				if (!options.keepRelativeSources) {
+					map.sources = results.map(res => res.source);
+				}
+				map.sourcesContent = results.map(res => res.content);
+				callback(null, input.replace(match[0], ""), map);
+			});
 	}
 }
diff --git a/package-lock.json b/package-lock.json
index 98b8845..66f216c 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -61,14 +61,6 @@
       "integrity": "sha1-iYUI2iIm84DfkEcoRWhJwVAaSw0=",
       "dev": true
     },
-    "async": {
-      "version": "2.5.0",
-      "resolved": "https://registry.npmjs.org/async/-/async-2.5.0.tgz",
-      "integrity": "sha512-e+lJAJeNWuPCNyxZKOBdaJGyLGHugXVQtrAwtuAe2vhxTYxFTKE73p8JuTmdH0qdQZtDvI4dhJwjZc5zsfIsYw==",
-      "requires": {
-        "lodash": "^4.14.0"
-      }
-    },
     "balanced-match": {
       "version": "1.0.0",
       "resolved": "https://registry.npmjs.org/balanced-match/-/balanced-match-1.0.0.tgz",
@@ -1030,7 +1022,7 @@
     },
     "json5": {
       "version": "0.5.1",
-      "resolved": "https://registry.npmjs.org/json5/-/json5-0.5.1.tgz",
+      "resolved": "http://registry.npmjs.org/json5/-/json5-0.5.1.tgz",
       "integrity": "sha1-Hq3nrMASA0rYTiOWdn6tn6VJWCE="
     },
     "jsonparse": {
@@ -1099,7 +1091,8 @@
     "lodash": {
       "version": "4.17.10",
       "resolved": "https://registry.npmjs.org/lodash/-/lodash-4.17.10.tgz",
-      "integrity": "sha512-UejweD1pDoXu+AD825lWwp4ZGtSwgnpZxb3JDViD7StjQz+Nb/6l093lx4OQ0foGWNRoc19mWy7BzL+UAK2iVg=="
+      "integrity": "sha512-UejweD1pDoXu+AD825lWwp4ZGtSwgnpZxb3JDViD7StjQz+Nb/6l093lx4OQ0foGWNRoc19mWy7BzL+UAK2iVg==",
+      "dev": true
     },
     "lodash._reinterpolate": {
       "version": "3.0.0",
diff --git a/package.json b/package.json
index 83e35e7..d55c20e 100644
--- a/package.json
+++ b/package.json
@@ -12,7 +12,6 @@
     "release": "standard-version"
   },
   "dependencies": {
-    "async": "^2.5.0",
     "loader-utils": "^1.1.0"
   },
   "devDependencies": {
diff --git a/test/fixtures/null-sourcesContent-source-map.js b/test/fixtures/null-sourcesContent-source-map.js
new file mode 100644
index 0000000..3c5c45d
--- /dev/null
+++ b/test/fixtures/null-sourcesContent-source-map.js
@@ -0,0 +1,2 @@
+with SourceMap
+//#sourceMappingURL=null-sourcesContent-source-map.map
\ No newline at end of file
diff --git a/test/fixtures/null-sourcesContent-source-map.map b/test/fixtures/null-sourcesContent-source-map.map
new file mode 100644
index 0000000..4a37daf
--- /dev/null
+++ b/test/fixtures/null-sourcesContent-source-map.map
@@ -0,0 +1 @@
+{"version":3,"file":"null-sourcesContent-source-map.js","sources":["null-sourcesContent-source-map.txt"],"sourcesContent":[null],"mappings":"AAAA"}
\ No newline at end of file
diff --git a/test/fixtures/null-sourcesContent-source-map.txt b/test/fixtures/null-sourcesContent-source-map.txt
new file mode 100644
index 0000000..3f2f36d
--- /dev/null
+++ b/test/fixtures/null-sourcesContent-source-map.txt
@@ -0,0 +1 @@
+with SourceMap
\ No newline at end of file
diff --git a/test/fixtures/relative-sourceRoot-sourcesContent-source-map.js b/test/fixtures/relative-sourceRoot-sourcesContent-source-map.js
new file mode 100644
index 0000000..cbd9fc1
--- /dev/null
+++ b/test/fixtures/relative-sourceRoot-sourcesContent-source-map.js
@@ -0,0 +1,2 @@
+with SourceMap
+//#sourceMappingURL=relative-sourceRoot-sourcesContent-source-map.map
\ No newline at end of file
diff --git a/test/fixtures/relative-sourceRoot-sourcesContent-source-map.map b/test/fixtures/relative-sourceRoot-sourcesContent-source-map.map
new file mode 100644
index 0000000..b103a97
--- /dev/null
+++ b/test/fixtures/relative-sourceRoot-sourcesContent-source-map.map
@@ -0,0 +1 @@
+{"version":3,"file":"relative-sourceRoot-sourcesContent-source-map.js","sourceRoot":"../fixtures/data/","sources":["relative-sourceRoot-sourcesContent-source-map.txt"],"sourcesContent":["with SourceMap"],"mappings":"AAAA"}
\ No newline at end of file
diff --git a/test/index.test.js b/test/index.test.js
index 1191e24..308bcf9 100644
--- a/test/index.test.js
+++ b/test/index.test.js
@@ -3,21 +3,12 @@ var fs = require("fs");
 var should = require("should");
 var loader = require("../");
 
-function execLoader(filename, callback) {
+const execLoader = (filename) => new Promise((resolvePromise, rejectPromise) => {
 	var async = false;
 	var deps = [];
 	var warns = [];
 	var context = {
 		context: path.dirname(filename),
-		resolve: function(context, request, callback) {
-			process.nextTick(function() {
-				var p = path.isAbsolute(request) ? request : path.resolve(context, request);
-				if(fs.existsSync(p))
-					callback(null, p);
-				else
-					callback(new Error("File not found"));
-			});
-		},
 		addDependency: function(dep) {
 			deps.push(dep);
 		},
@@ -26,7 +17,11 @@ function execLoader(filename, callback) {
 		},
 		callback: function(err, res, map) {
 			async = true;
-			callback(err, res, map, deps, warns);
+			if(err) {
+				rejectPromise(err);
+			} else {
+				resolvePromise({res, map, deps, warns});
+			}
 		},
 		async: function() {
 			async = true;
@@ -36,199 +31,188 @@ function execLoader(filename, callback) {
 	// Remove CRs to make test line ending invariant
 	var fixtureContent = fs.readFileSync(filename, "utf-8").replace(/\r/g, '');
 	var res = loader.call(context, fixtureContent);
-	if(!async) return callback(null, res, null, deps, warns);
-}
+	if(!async) return resolvePromise({res, map: null, deps, warns});
+});
 
 describe("source-map-loader", function() {
 	const fixturesPath = path.join(__dirname, "fixtures");
 	const dataPath = path.join(fixturesPath, "data");
 
-	it("should leave normal files untouched", function(done) {
-		execLoader(path.join(fixturesPath, "normal-file.js"), function(err, res, map, deps, warns) {
-			should.equal(err, null);
-			warns.should.be.eql([]);
-			should.equal(res, "without SourceMap"),
-			should.equal(map, null);
-			deps.should.be.eql([]);
-			done();
-		});
-	});
-
-	it("should process inlined SourceMaps", function(done) {
-		execLoader(path.join(fixturesPath, "inline-source-map.js"), function(err, res, map, deps, warns) {
-			should.equal(err, null);
-			warns.should.be.eql([]);
-			should.equal(res, "with SourceMap\n// comment"),
-			map.should.be.eql({
-				"version":3,
-				"file":"inline-source-map.js",
-				"sources":[
-					"inline-source-map.txt"
-				],
-				"sourcesContent":["with SourceMap"],
-				"mappings":"AAAA"
+	it("should leave normal files untouched", function() {
+		return execLoader(path.join(fixturesPath, "normal-file.js"))
+			.then(function({res, map, deps, warns}) {
+				warns.should.be.eql([]);
+				should.equal(res, "without SourceMap");
+				should.equal(map, null);
+				deps.should.be.eql([]);
 			});
-			deps.should.be.eql([]);
-			done();
-		});
 	});
 
-	it("should process external SourceMaps", function(done) {
-		execLoader(path.join(fixturesPath, "external-source-map.js"), function(err, res, map, deps, warns) {
-			should.equal(err, null);
-			warns.should.be.eql([]);
-			should.equal(res, "with SourceMap\n// comment"),
-			map.should.be.eql({
-				"version":3,
-				"file":"external-source-map.js",
-				"sources":[
-					"external-source-map.txt"
-				],
-				"sourcesContent":["with SourceMap"],
-				"mappings":"AAAA"
+	it("should process inlined SourceMaps", function() {
+		return execLoader(path.join(fixturesPath, "inline-source-map.js"))
+			.then(function({res, map, deps, warns}) {
+				warns.should.be.eql([]);
+				should.equal(res, "with SourceMap\n// comment");
+				map.should.be.eql({
+					"version":3,
+					"file":"inline-source-map.js",
+					"sources":[
+						path.join(fixturesPath,"inline-source-map.txt")
+					],
+					"sourcesContent":["with SourceMap"],
+					"mappings":"AAAA"
+				});
+				deps.should.be.eql([]);
 			});
-			deps.should.be.eql([
-				path.join(fixturesPath, "external-source-map.map")
-			]);
-			done();
-		});
 	});
 
-	it("should process external SourceMaps (external sources)", function(done) {
-		execLoader(path.join(fixturesPath, "external-source-map2.js"), function(err, res, map, deps, warns) {
-			should.equal(err, null);
-			warns.should.be.eql([]);
-			should.equal(res, "with SourceMap\n// comment"),
-			map.should.be.eql({
-				"version":3,
-				"file":"external-source-map2.js",
-				"sources":[
-					path.join(fixturesPath, "external-source-map2.txt")
-				],
-				"sourcesContent":["with SourceMap"],
-				"mappings":"AAAA"
+	it("should process external SourceMaps", function() {
+		return execLoader(path.join(fixturesPath, "external-source-map.js"))
+			.then(function({res, map, deps, warns}) {
+				warns.should.be.eql([]);
+				should.equal(res, "with SourceMap\n// comment");
+				map.should.be.eql({
+					"version":3,
+					"file":"external-source-map.js",
+					"sources":[
+						path.join(fixturesPath,"external-source-map.txt")
+					],
+					"sourcesContent":["with SourceMap"],
+					"mappings":"AAAA"
+				});
+				deps.should.be.eql([
+					path.join(fixturesPath, "external-source-map.map")
+				]);
 			});
-			deps.should.be.eql([
-				path.join(dataPath, "external-source-map2.map"),
-				path.join(fixturesPath, "external-source-map2.txt")
-			]);
-			done();
-		});
 	});
 
-	it("should use last SourceMap directive", function (done) {
-		execLoader(path.join(fixturesPath, "multi-source-map.js"), function (err, res, map, deps, warns) {
-			should.equal(err, null);
-			warns.should.be.eql([]);
-			should.equal(res, "with SourceMap\nanInvalidDirective = \"\\n/*# sourceMappingURL=data:application/json;base64,\"+btoa(unescape(encodeURIComponent(JSON.stringify(sourceMap))))+\" */\";\n// comment"),
+	it("should process external SourceMaps (external sources)", function() {
+		return execLoader(path.join(fixturesPath, "external-source-map2.js"))
+			.then(function({res, map, deps, warns}) {
+				warns.should.be.eql([]);
+				should.equal(res, "with SourceMap\n// comment");
 				map.should.be.eql({
-					"version": 3,
-					"file": "inline-source-map.js",
-					"sources": [
-						"inline-source-map.txt"
+					"version":3,
+					"file":"external-source-map2.js",
+					"sources":[
+						path.join(fixturesPath, "external-source-map2.txt")
 					],
-					"sourcesContent": ["with SourceMap"],
-					"mappings": "AAAA"
+					"sourcesContent":["with SourceMap"],
+					"mappings":"AAAA"
 				});
-			deps.should.be.eql([]);
-			done();
-		});
+				deps.should.be.eql([
+					path.join(dataPath, "external-source-map2.map"),
+					path.join(fixturesPath, "external-source-map2.txt")
+				]);
+			});
 	});
 
-	it("should skip invalid base64 SourceMap", function (done) {
-		execLoader(path.join(fixturesPath, "invalid-inline-source-map.js"), function (err, res, map, deps, warns) {
-			should.equal(err, null);
-			warns.should.be.eql([]);
-			should.equal(res, "without SourceMap\n// @sourceMappingURL=data:application/source-map;base64,\"something invalid\"\n// comment");
-			should.equal(map, null);
-			deps.should.be.eql([]);
-			done();
-		});
+	it("should use last SourceMap directive", function () {
+		return execLoader(path.join(fixturesPath, "multi-source-map.js"))
+			.then(function({res, map, deps, warns}) {
+				warns.should.be.eql([]);
+				should.equal(res, "with SourceMap\nanInvalidDirective = \"\\n/*# sourceMappingURL=data:application/json;base64,\"+btoa(unescape(encodeURIComponent(JSON.stringify(sourceMap))))+\" */\";\n// comment");
+					map.should.be.eql({
+						"version": 3,
+						"file": "inline-source-map.js",
+						"sources": [
+							path.join(fixturesPath,"inline-source-map.txt")
+						],
+						"sourcesContent": ["with SourceMap"],
+						"mappings": "AAAA"
+					});
+				deps.should.be.eql([]);
+			});
 	});
-	it("should warn on invalid base64 SourceMap", function (done) {
-		execLoader(path.join(fixturesPath, "invalid-inline-source-map2.js"), function (err, res, map, deps, warns) {
-			should.equal(err, null);
-			warns.should.matchEach(
-				new RegExp("Cannot parse inline SourceMap 'invalid\/base64=': SyntaxError: Unexpected token")
-			);
-			should.equal(res, "without SourceMap\n// @sourceMappingURL=data:application/source-map;base64,invalid/base64=\n// comment");
-			should.equal(map, null);
-			deps.should.be.eql([]);
-			done();
-		});
+
+	it("should skip invalid base64 SourceMap", function () {
+		return execLoader(path.join(fixturesPath, "invalid-inline-source-map.js"))
+			.then(function({res, map, deps, warns}) {
+				warns.should.be.eql([]);
+				should.equal(res, "without SourceMap\n// @sourceMappingURL=data:application/source-map;base64,\"something invalid\"\n// comment");
+				should.equal(map, null);
+				deps.should.be.eql([]);
+			});
+	});
+	it("should warn on invalid base64 SourceMap", function () {
+		return execLoader(path.join(fixturesPath, "invalid-inline-source-map2.js"))
+			.then(function({res, map, deps, warns}) {
+				warns.should.matchEach(
+					new RegExp("Cannot parse inline SourceMap 'invalid\/base64=': SyntaxError: Unexpected token")
+				);
+				should.equal(res, "without SourceMap\n// @sourceMappingURL=data:application/source-map;base64,invalid/base64=\n// comment");
+				should.equal(map, null);
+				deps.should.be.eql([]);
+			});
 	});
 
-	it("should warn on invalid SourceMap", function (done) {
-		execLoader(path.join(fixturesPath, "invalid-source-map.js"), function (err, res, map, deps, warns) {
-			should.equal(err, null);
-			warns.should.matchEach(
-				new RegExp("Cannot parse SourceMap 'invalid-source-map.map': SyntaxError: Unexpected string in JSON at position 102")
-			);
-			should.equal(res, "with SourceMap\n//#sourceMappingURL=invalid-source-map.map\n// comment");
-			should.equal(map, null);
-			deps.should.be.eql([
-				path.join(fixturesPath, "invalid-source-map.map")
-			]);
-			done();
-		});
+	it("should warn on invalid SourceMap", function () {
+		return execLoader(path.join(fixturesPath, "invalid-source-map.js"))
+			.then(function({res, map, deps, warns}) {
+				warns.should.matchEach(
+					new RegExp("Cannot parse SourceMap 'invalid-source-map.map': SyntaxError: Unexpected string in JSON at position 102")
+				);
+				should.equal(res, "with SourceMap\n//#sourceMappingURL=invalid-source-map.map\n// comment");
+				should.equal(map, null);
+				deps.should.be.eql([
+					path.join(fixturesPath, "invalid-source-map.map")
+				]);
+			});
 	});
 
-	it("should warn on missing SourceMap", function(done) {
-		execLoader(path.join(fixturesPath, "missing-source-map.js"), function(err, res, map, deps, warns) {
-			should.equal(err, null);
-			warns.should.be.eql([
-				"Cannot find SourceMap 'missing-source-map.map': Error: File not found"
-			]);
-			should.equal(res, "with SourceMap\n//#sourceMappingURL=missing-source-map.map\n// comment"),
-			should.equal(map, null);
-			deps.should.be.eql([]);
-			done();
-		});
+	it("should warn on missing SourceMap", function() {
+		return execLoader(path.join(fixturesPath, "missing-source-map.js"))
+			.then(function({res, map, deps, warns}) {
+				warns.should.matchEach(
+					new RegExp(`Cannot open SourceMap '${path.join(fixturesPath, 'missing-source-map.map')}':`)
+				);
+				should.equal(res, "with SourceMap\n//#sourceMappingURL=missing-source-map.map\n// comment");
+				should.equal(map, null);
+				deps.should.be.eql([]);
+			});
 	});
 
-	it("should warn on missing source file", function(done) {
-		execLoader(path.join(fixturesPath, "missing-source-map2.js"), function(err, res, map, deps, warns) {
-			should.equal(err, null);
-			warns.should.be.eql([
-				"Cannot find source file 'missing-source-map2.txt': Error: File not found"
-			]);
-			should.equal(res, "with SourceMap\n// comment"),
-			map.should.be.eql({
-				"version":3,
-				"file":"missing-source-map2.js",
-				"sources":[
-					"missing-source-map2.txt"
-				],
-				"sourcesContent":[null],
-				"mappings":"AAAA"
+	it("should warn on missing source file", function() {
+		return execLoader(path.join(fixturesPath, "missing-source-map2.js"))
+			.then(function({res, map, deps, warns}) {
+				warns.should.matchEach(
+					new RegExp(`Cannot open source file '${path.join(fixturesPath, 'missing-source-map2.txt')}':`)
+				);
+				should.equal(res, "with SourceMap\n// comment");
+				map.should.be.eql({
+					"version":3,
+					"file":"missing-source-map2.js",
+					"sources":[
+						path.join(fixturesPath,"missing-source-map2.txt")
+					],
+					"sourcesContent":[null],
+					"mappings":"AAAA"
+				});
+				deps.should.be.eql([
+					path.join(fixturesPath, "missing-source-map2.map")
+				]);
 			});
-			deps.should.be.eql([
-				path.join(fixturesPath, "missing-source-map2.map")
-			]);
-			done();
-		});
 	});
 
-	it("should process inlined SourceMaps with charset", function(done) {
-		execLoader(path.join(fixturesPath, "charset-inline-source-map.js"), function(err, res, map, deps, warns) {
-			should.equal(err, null);
-			warns.should.be.eql([]);
-			should.equal(res, "with SourceMap\n// comment"),
-			map.should.be.eql({
-				"version":3,
-				"file":"charset-inline-source-map.js",
-				"sources":[
-					"charset-inline-source-map.txt"
-				],
-				"sourcesContent":["with SourceMap"],
-				"mappings":"AAAA"
+	it("should process inlined SourceMaps with charset", function() {
+		return execLoader(path.join(fixturesPath, "charset-inline-source-map.js"))
+			.then(function({res, map, deps, warns}) {
+				warns.should.be.eql([]);
+				should.equal(res, "with SourceMap\n// comment");
+				map.should.be.eql({
+					"version":3,
+					"file":"charset-inline-source-map.js",
+					"sources":[
+						path.join(fixturesPath,"charset-inline-source-map.txt")
+					],
+					"sourcesContent":["with SourceMap"],
+					"mappings":"AAAA"
+				});
+				deps.should.be.eql([]);
 			});
-			deps.should.be.eql([]);
-			done();
-		});
 	});
 
-	it("should support absolute sourceRoot paths in sourcemaps", (done) => {
+	it("should support absolute sourceRoot paths in sourcemaps", () => {
 		const sourceRoot = path.join(fixturesPath);
 		const javaScriptFilename = "absolute-sourceRoot-source-map.js";
 		const sourceFilename = "absolute-sourceRoot-source-map.txt";
@@ -247,12 +231,10 @@ describe("source-map-loader", function() {
 		};
 		fs.writeFileSync(sourceMapPath, JSON.stringify(rawSourceMap));
 
-		execLoader(
-			path.join(fixturesPath, javaScriptFilename),
-			(err, res, map, deps, warns) => {
-				should.equal(err, null);
+		return execLoader(path.join(fixturesPath, javaScriptFilename))
+			.then(function({res, map, deps, warns}) {
 				warns.should.be.eql([]);
-				should.equal(res, "with SourceMap\n// comment"),
+				should.equal(res, "with SourceMap\n// comment");
 				map.should.be.eql({
 					"version": 3,
 					"file": javaScriptFilename,
@@ -268,23 +250,20 @@ describe("source-map-loader", function() {
 					sourceMapPath,
 					rootRelativeSourcePath
 				]);
-				done();
 			}
 		);
 	});
 
-	it("should support relative sourceRoot paths in sourcemaps", (done) => {
+	it("should support relative sourceRoot paths in sourcemaps", () => {
 		const javaScriptFilename = "relative-sourceRoot-source-map.js";
 		const sourceFilename = "relative-sourceRoot-source-map.txt";
 		const rootRelativeSourcePath = path.join(dataPath, sourceFilename);
 		const sourceMapPath = path.join(fixturesPath, "relative-sourceRoot-source-map.map");
 
-		execLoader(
-			path.join(fixturesPath, javaScriptFilename),
-			(err, res, map, deps, warns) => {
-				should.equal(err, null);
+		return execLoader(path.join(fixturesPath, javaScriptFilename))
+			.then(function({res, map, deps, warns}) {
 				warns.should.be.eql([]);
-				should.equal(res, "with SourceMap\n// comment"),
+				should.equal(res, "with SourceMap\n// comment");
 				map.should.be.eql({
 					"version": 3,
 					"file": javaScriptFilename,
@@ -300,7 +279,63 @@ describe("source-map-loader", function() {
 					sourceMapPath,
 					rootRelativeSourcePath
 				]);
-				done();
+			}
+		);
+	});
+
+	it("should support null value in sourcesContent", () => {
+		const javaScriptFilename = "null-sourcesContent-source-map.js";
+		const sourceFilename = "null-sourcesContent-source-map.txt";
+		const rootRelativeSourcePath = path.join(fixturesPath, sourceFilename);
+		const sourceMapPath = path.join(fixturesPath, "null-sourcesContent-source-map.map");
+
+		return execLoader(path.join(fixturesPath, javaScriptFilename))
+			.then(function({res, map, deps, warns}) {
+				warns.should.be.eql([]);
+				should.equal(res, "with SourceMap\n");
+				map.should.be.eql({
+					"version": 3,
+					"file": javaScriptFilename,
+					"sources": [
+						rootRelativeSourcePath
+					],
+					"sourcesContent": [
+						"with SourceMap"
+					],
+					"mappings": "AAAA"
+				});
+				deps.should.be.eql([
+					sourceMapPath,
+					rootRelativeSourcePath
+				]);
+			}
+		);
+	});
+
+	it("should resolve relative sources path even with sourcesContent", () => {
+		const javaScriptFilename = "relative-sourceRoot-sourcesContent-source-map.js";
+		const sourceFilename = "relative-sourceRoot-sourcesContent-source-map.txt";
+		const rootRelativeSourcePath = path.join(dataPath, sourceFilename);
+		const sourceMapPath = path.join(fixturesPath, "relative-sourceRoot-sourcesContent-source-map.map");
+
+		return execLoader(path.join(fixturesPath, javaScriptFilename))
+			.then(function({res, map, deps, warns}) {
+				warns.should.be.eql([]);
+				should.equal(res, "with SourceMap\n");
+				map.should.be.eql({
+					"version": 3,
+					"file": javaScriptFilename,
+					"sources": [
+						rootRelativeSourcePath
+					],
+					"sourcesContent": [
+						"with SourceMap"
+					],
+					"mappings": "AAAA"
+				});
+				deps.should.be.eql([
+					sourceMapPath
+				]);
 			}
 		);
 	});