diff --git a/package-lock.json b/package-lock.json
index 676374a..79a83e1 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -12069,7 +12069,8 @@
     "neo-async": {
       "version": "2.6.1",
       "resolved": "https://registry.npmjs.org/neo-async/-/neo-async-2.6.1.tgz",
-      "integrity": "sha512-iyam8fBuCUpWeKPGpaNMetEocMt364qkCsfL9JuhjXX6dRnguRVOfk2GZaDpPjcOKiiXCPINZC1GczQ7iTq3Zw=="
+      "integrity": "sha512-iyam8fBuCUpWeKPGpaNMetEocMt364qkCsfL9JuhjXX6dRnguRVOfk2GZaDpPjcOKiiXCPINZC1GczQ7iTq3Zw==",
+      "dev": true
     },
     "nice-try": {
       "version": "1.0.5",
diff --git a/package.json b/package.json
index 0572eaf..d6ba112 100644
--- a/package.json
+++ b/package.json
@@ -43,7 +43,6 @@
   "dependencies": {
     "data-urls": "^2.0.0",
     "loader-utils": "^2.0.0",
-    "neo-async": "^2.6.1",
     "schema-utils": "^2.6.6",
     "source-map": "^0.6.0",
     "whatwg-encoding": "^1.0.5"
diff --git a/src/index.js b/src/index.js
index 303a9a9..5ff0623 100644
--- a/src/index.js
+++ b/src/index.js
@@ -6,14 +6,13 @@ import fs from 'fs';
 import path from 'path';
 
 import validateOptions from 'schema-utils';
-import async from 'neo-async';
 import parseDataURL from 'data-urls';
+import { SourceMapConsumer } from 'source-map';
 import { labelToName, decode } from 'whatwg-encoding';
 import { getOptions, urlToRequest } from 'loader-utils';
 
-import flattenSourceMap from './utils/flatten';
-
 import schema from './options.json';
+import { flattenSourceMap, normalize, MapAgregator } from './utils';
 
 // Matches only the last occurrence of sourceMappingURL
 const baseRegex =
@@ -121,70 +120,68 @@ export default function loader(input, inputMap) {
       map = await flattenSourceMap(map);
     }
 
-    if (map.sourcesContent && map.sourcesContent.length >= map.sources.length) {
-      callback(null, input.replace(match[0], ''), map);
-
-      return;
-    }
-
-    const sourcePrefix = map.sourceRoot ? `${map.sourceRoot}${path.sep}` : '';
-
-    // eslint-disable-next-line no-param-reassign
-    map.sources = map.sources.map((s) => sourcePrefix + s);
-
-    // eslint-disable-next-line no-param-reassign
-    delete map.sourceRoot;
-
-    const missingSources = map.sourcesContent
-      ? map.sources.slice(map.sourcesContent.length)
-      : map.sources;
-
-    async.map(
-      missingSources,
-      // eslint-disable-next-line no-shadow
-      (source, callback) => {
-        resolve(context, urlToRequest(source, true), (resolveError, result) => {
-          if (resolveError) {
-            emitWarning(`Cannot find source file '${source}': ${resolveError}`);
+    const mapConsumer = await new SourceMapConsumer(map);
+
+    const resolvedSources = await Promise.all(
+      map.sources.map(async (source) => {
+        const fullPath = map.sourceRoot
+          ? `${map.sourceRoot}/${source}`
+          : source;
+        const sourceData = new MapAgregator({
+          mapConsumer,
+          source,
+          fullPath,
+          emitWarning,
+        });
 
-            callback(null, null);
+        if (path.isAbsolute(fullPath)) {
+          return sourceData.content;
+        }
+
+        return new Promise((promiseResolve) => {
+          resolve(
+            context,
+            urlToRequest(fullPath, true),
+            (resolveError, result) => {
+              if (resolveError) {
+                emitWarning(
+                  `Cannot find source file '${source}': ${resolveError}`
+                );
+
+                return promiseResolve(sourceData.placeholderContent);
+              }
+
+              sourceData.setFullPath(result);
+              return promiseResolve(sourceData.content);
+            }
+          );
+        });
+      })
+    );
 
-            return;
-          }
+    const resultMap = { ...map };
+    resultMap.sources = [];
+    resultMap.sourcesContent = [];
 
-          addDependency(result);
+    delete resultMap.sourceRoot;
 
-          fs.readFile(result, 'utf-8', (readFileError, content) => {
-            if (readFileError) {
-              emitWarning(
-                `Cannot open source file '${result}': ${readFileError}`
-              );
+    resolvedSources.forEach((res) => {
+      // eslint-disable-next-line no-param-reassign
+      resultMap.sources.push(normalize(res.source));
+      resultMap.sourcesContent.push(res.content);
 
-              callback(null, null);
+      if (res.source) {
+        addDependency(res.source);
+      }
+    });
 
-              return;
-            }
+    const sourcesContentIsEmpty =
+      resultMap.sourcesContent.filter((entry) => !!entry).length === 0;
 
-            callback(null, { source: result, content });
-          });
-        });
-      },
-      (err, info) => {
-        // eslint-disable-next-line no-param-reassign
-        map.sourcesContent = map.sourcesContent || [];
-
-        info.forEach((res) => {
-          if (res) {
-            // eslint-disable-next-line no-param-reassign
-            map.sources[map.sourcesContent.length] = res.source;
-            map.sourcesContent.push(res.content);
-          } else {
-            map.sourcesContent.push(null);
-          }
-        });
+    if (sourcesContentIsEmpty) {
+      delete resultMap.sourcesContent;
+    }
 
-        processMap(map, context, callback);
-      }
-    );
+    callback(null, input.replace(match[0], ''), resultMap);
   }
 }
diff --git a/src/utils.js b/src/utils.js
new file mode 100644
index 0000000..af3a43b
--- /dev/null
+++ b/src/utils.js
@@ -0,0 +1,90 @@
+import fs from 'fs';
+
+import sourceMap from 'source-map';
+
+async function flattenSourceMap(map) {
+  const consumer = await new sourceMap.SourceMapConsumer(map);
+  let generatedMap;
+
+  if (map.file) {
+    generatedMap = new sourceMap.SourceMapGenerator({
+      file: map.file,
+    });
+  } else {
+    generatedMap = new sourceMap.SourceMapGenerator();
+  }
+
+  consumer.sources.forEach((sourceFile) => {
+    const sourceContent = consumer.sourceContentFor(sourceFile, true);
+    generatedMap.setSourceContent(sourceFile, sourceContent);
+  });
+
+  consumer.eachMapping((mapping) => {
+    const { source } = consumer.originalPositionFor({
+      line: mapping.generatedLine,
+      column: mapping.generatedColumn,
+    });
+
+    const mappings = {
+      source,
+      original: {
+        line: mapping.originalLine,
+        column: mapping.originalColumn,
+      },
+      generated: {
+        line: mapping.generatedLine,
+        column: mapping.generatedColumn,
+      },
+    };
+
+    if (source) {
+      generatedMap.addMapping(mappings);
+    }
+  });
+
+  return generatedMap.toJSON();
+}
+
+function normalize(path) {
+  return path.replace(/\\/g, '/');
+}
+
+function readFile(fullPath, charset, emitWarning) {
+  return new Promise((resolve) => {
+    fs.readFile(fullPath, charset, (readFileError, content) => {
+      if (readFileError) {
+        emitWarning(`Cannot open source file '${fullPath}': ${readFileError}`);
+
+        resolve({ source: fullPath, content: null });
+      }
+
+      resolve({ source: fullPath, content });
+    });
+  });
+}
+
+class MapAgregator {
+  constructor({ mapConsumer, source, fullPath, emitWarning }) {
+    this.fullPath = fullPath;
+    this.sourceContent = mapConsumer.sourceContentFor(source, true);
+    this.emitWarning = emitWarning;
+  }
+
+  setFullPath(path) {
+    this.fullPath = path;
+  }
+
+  get content() {
+    return this.sourceContent
+      ? { source: this.fullPath, content: this.sourceContent }
+      : readFile(this.fullPath, 'utf-8', this.emitWarning);
+  }
+
+  get placeholderContent() {
+    return this.sourceContent
+      ? { source: this.fullPath, content: this.sourceContent }
+      : { source: this.fullPath, content: null };
+  }
+}
+
+export { flattenSourceMap, normalize, MapAgregator };
diff --git a/src/utils/flatten.js b/src/utils/flatten.js
deleted file mode 100644
index 0003eff..0000000
--- a/src/utils/flatten.js
+++ /dev/null
@@ -1,46 +0,0 @@
-import sourceMap from 'source-map';
-
-async function FlattenSourceMap(map) {
-  const consumer = await new sourceMap.SourceMapConsumer(map);
-  let generatedMap;
-
-  if (map.file) {
-    generatedMap = new sourceMap.SourceMapGenerator({
-      file: map.file,
-    });
-  } else {
-    generatedMap = new sourceMap.SourceMapGenerator();
-  }
-
-  consumer.sources.forEach((sourceFile) => {
-    const sourceContent = consumer.sourceContentFor(sourceFile, true);
-    generatedMap.setSourceContent(sourceFile, sourceContent);
-  });
-
-  consumer.eachMapping((mapping) => {
-    const { source } = consumer.originalPositionFor({
-      line: mapping.generatedLine,
-      column: mapping.generatedColumn,
-    });
-
-    const mappings = {
-      source,
-      original: {
-        line: mapping.originalLine,
-        column: mapping.originalColumn,
-      },
-      generated: {
-        line: mapping.generatedLine,
-        column: mapping.generatedColumn,
-      },
-    };
-
-    if (source) {
-      generatedMap.addMapping(mappings);
-    }
-  });
-
-  return generatedMap.toJSON();
-}
-
-module.exports = FlattenSourceMap;
diff --git a/test/__snapshots__/loader.test.js.snap b/test/__snapshots__/loader.test.js.snap
index 78dce75..0f9f84f 100644
--- a/test/__snapshots__/loader.test.js.snap
+++ b/test/__snapshots__/loader.test.js.snap
@@ -50,7 +50,12 @@ Object {
 }
 `;
 
-exports[`source-map-loader should process external SourceMaps: warnings 1`] = `Array []`;
+exports[`source-map-loader should process external SourceMaps: warnings 1`] = `
+Array [
+  "ModuleWarning: Module Warning (from \`replaced original path\`):
+(Emitted value instead of an instance of Error) Cannot find source file 'external-source-map.txt': Error: Can't resolve './external-source-map.txt' in '/test/fixtures'",
+]
+`;
 
 exports[`source-map-loader should process inlined SourceMaps with charset: css 1`] = `
 "with SourceMap
@@ -64,7 +69,7 @@ Object {
   "file": "charset-inline-source-map.js",
   "mappings": "AAAA",
   "sources": Array [
-    "charset-inline-source-map.txt",
+    "/test/fixtures/charset-inline-source-map.txt - (normalized for test)",
   ],
   "sourcesContent": Array [
     "with SourceMap",
@@ -96,7 +101,12 @@ Object {
 }
 `;
 
-exports[`source-map-loader should process inlined SourceMaps: warnings 1`] = `Array []`;
+exports[`source-map-loader should process inlined SourceMaps: warnings 1`] = `
+Array [
+  "ModuleWarning: Module Warning (from \`replaced original path\`):
+(Emitted value instead of an instance of Error) Cannot find source file 'inline-source-map.txt': Error: Can't resolve './inline-source-map.txt' in '/test/fixtures'",
+]
+`;
 
 exports[`source-map-loader should skip invalid base64 SourceMap: css 1`] = `
 "without SourceMap
@@ -133,7 +143,7 @@ Object {
 exports[`source-map-loader should support absolute sourceRoot paths in sourcemaps: warnings 1`] = `Array []`;
 
 exports[`source-map-loader should support indexed sourcemaps: css 1`] = `
-"with SourceMap
+"console.log('with SourceMap')
 // Map taken from here
 // https://github.com/mozilla/source-map/blob/master/test/util.js - indexedTestMapDifferentSourceRoots
 "
@@ -147,7 +157,7 @@ Object {
   "mappings": "CAAC,IAAI,IAAM,SAAU,GAClB,OAAO,IAAI;CCDb,IAAI,IAAM,SAAU,GAClB,OAAO",
   "names": Array [],
   "sources": Array [
-    "/the/root/nested1.js",
+    "/test/fixtures/indexed-sourcemap/nested1.js - (normalized for test)",
     "/different/root/nested2.js",
   ],
   "sourcesContent": Array [
@@ -210,7 +220,12 @@ Object {
 }
 `;
 
-exports[`source-map-loader should use last SourceMap directive: warnings 1`] = `Array []`;
+exports[`source-map-loader should use last SourceMap directive: warnings 1`] = `
+Array [
+  "ModuleWarning: Module Warning (from \`replaced original path\`):
+(Emitted value instead of an instance of Error) Cannot find source file 'inline-source-map.txt': Error: Can't resolve './inline-source-map.txt' in '/test/fixtures'",
+]
+`;
 
 exports[`source-map-loader should warn on invalid SourceMap: css 1`] = `
 "with SourceMap
@@ -271,9 +286,6 @@ Object {
   "sources": Array [
     "missing-source-map2.txt",
   ],
-  "sourcesContent": Array [
-    null,
-  ],
   "version": 3,
 }
 `;
diff --git a/test/fixtures/charset-inline-source-map.txt b/test/fixtures/charset-inline-source-map.txt
new file mode 100644
index 0000000..c5b4408
--- /dev/null
+++ b/test/fixtures/charset-inline-source-map.txt
@@ -0,0 +1 @@
+// Content
diff --git a/test/fixtures/indexed-sourcemap/file.js b/test/fixtures/indexed-sourcemap/file.js
index 2be7348..83076fd 100644
--- a/test/fixtures/indexed-sourcemap/file.js
+++ b/test/fixtures/indexed-sourcemap/file.js
@@ -1,4 +1,4 @@
-with SourceMap
+console.log('with SourceMap')
 //#sourceMappingURL=file.js.map
 // Map taken from here
 // https://github.com/mozilla/source-map/blob/master/test/util.js - indexedTestMapDifferentSourceRoots
diff --git a/test/fixtures/indexed-sourcemap/file.js.map b/test/fixtures/indexed-sourcemap/file.js.map
index 1dc44df..930cc52 100644
--- a/test/fixtures/indexed-sourcemap/file.js.map
+++ b/test/fixtures/indexed-sourcemap/file.js.map
@@ -15,8 +15,7 @@
         ],
         "names": ["bar", "baz"],
         "mappings": "CAAC,IAAI,IAAM,SAAUA,GAClB,OAAOC,IAAID",
-        "file": "file.js",
-        "sourceRoot": "/the/root"
+        "file": "file.js"
       }
     },
     {
diff --git a/test/helpers/getCompiler.js b/test/helpers/getCompiler.js
index b391311..6e34d5a 100644
--- a/test/helpers/getCompiler.js
+++ b/test/helpers/getCompiler.js
@@ -3,7 +3,25 @@ import path from 'path';
 import webpack from 'webpack';
 import { createFsFromVolume, Volume } from 'memfs';
 
-export default (fixture, loaderOptions = {}, config = {}) => {
+export default (
+  fixture,
+  loaderOptions = {},
+  config = {},
+  skipTestLoader = false
+) => {
+  const loaders = [
+    {
+      loader: path.resolve(__dirname, '../../src'),
+      options: loaderOptions || {},
+    },
+  ];
+
+  if (!skipTestLoader) {
+    loaders.unshift({
+      loader: require.resolve('./testLoader'),
+    });
+  }
+
   const fullConfig = {
     mode: 'development',
     devtool: config.devtool || 'source-map',
@@ -19,15 +37,7 @@ export default (fixture, loaderOptions = {}, config = {}) => {
       rules: [
         {
           test: /\.js/i,
-          rules: [
-            {
-              loader: require.resolve('./testLoader'),
-            },
-            {
-              loader: path.resolve(__dirname, '../../src'),
-              options: loaderOptions || {},
-            },
-          ],
+          use: loaders,
         },
       ],
     },
diff --git a/test/helpers/normalizeMap.js b/test/helpers/normalizeMap.js
index 89c0bf9..bc5b279 100644
--- a/test/helpers/normalizeMap.js
+++ b/test/helpers/normalizeMap.js
@@ -33,13 +33,6 @@ function removeCWD(str) {
   let cwd = process.cwd();
 
   if (isWin) {
-    // Todo: explore the issue
-    // if (str.includes('/')) {
-    //   throw new Error(
-    //     'There should not be a forward slash in the Windows path'
-    //   );
-    // }
-
     // eslint-disable-next-line no-param-reassign
     str = str.replace(/\\/g, '/');
     cwd = cwd.replace(/\\/g, '/');
diff --git a/test/loader.test.js b/test/loader.test.js
index e2261bf..04d21c3 100644
--- a/test/loader.test.js
+++ b/test/loader.test.js
@@ -8,6 +8,7 @@ import {
   getErrors,
   normalizeMap,
   getWarnings,
+  readAsset,
 } from './helpers';
 
 describe('source-map-loader', () => {
@@ -267,6 +268,8 @@ describe('source-map-loader', () => {
     const dependencies = [
       path.join(currentDirPath, 'file.js'),
       path.join(currentDirPath, 'file.js.map'),
+      path.join(currentDirPath, 'nested1.js'),
+      `/different/root/nested2.js`,
     ];
 
     dependencies.forEach((fixture) => {
@@ -278,4 +281,28 @@ describe('source-map-loader', () => {
     expect(getWarnings(stats)).toMatchSnapshot('warnings');
     expect(getErrors(stats)).toMatchSnapshot('errors');
   });
+
+  it('should transform to webpack', async () => {
+    const currentDirPath = path.join(
+      __dirname,
+      'fixtures',
+      'indexed-sourcemap'
+    );
+
+    const testId = path.join(currentDirPath, 'file.js');
+    const compiler = getCompiler(testId, {}, {}, true);
+    const stats = await compile(compiler);
+    const bundle = readAsset('main.bundle.js.map', compiler, stats);
+
+    const dependencies = [
+      'indexed-sourcemap/nested1.js',
+      'different/root/nested2.js',
+      'webpack/bootstrap',
+    ];
+
+    // Todo: rewrite when we will fix issue whith unresolved paths
+    dependencies.forEach((fixture) => {
+      expect(bundle.indexOf(fixture) !== -1).toBe(true);
+    });
+  });
 });