diff --git a/external/builder/preprocessor2.js b/external/builder/preprocessor2.js
index 9e9b5e3ab..2fc242b22 100644
--- a/external/builder/preprocessor2.js
+++ b/external/builder/preprocessor2.js
@@ -347,28 +347,23 @@ function traverseTree(ctx, node) {
 }
 
 function preprocessPDFJSCode(ctx, code) {
-  var saveComments = !!ctx.saveComments;
   var format = ctx.format || {
     indent: {
       style: ' ',
-      adjustMultilineComment: saveComments,
     }
   };
-  var comments;
-  var parseComment = {
+  var parseOptions = {
     locations: true,
-    onComments: saveComments || (comments = []),
+    sourceFile: ctx.sourceFile,
     sourceType: 'module',
   };
   var codegenOptions = {
     format: format,
-    comment: saveComments,
     parse: acorn.parse,
+    sourceMap: ctx.sourceMap,
+    sourceMapWithCode: ctx.sourceMap,
   };
-  var syntax = acorn.parse(code, parseComment);
-  if (saveComments) {
-    escodegen.attachComments(syntax, comments);
-  }
+  var syntax = acorn.parse(code, parseOptions);
   traverseTree(ctx, syntax);
   return escodegen.generate(syntax, codegenOptions);
 }
diff --git a/external/webpack/pdfjsdev-loader.js b/external/webpack/pdfjsdev-loader.js
index beba2a887..ca6cafee2 100644
--- a/external/webpack/pdfjsdev-loader.js
+++ b/external/webpack/pdfjsdev-loader.js
@@ -17,6 +17,7 @@
 'use strict';
 
 var preprocessor2 = require('../builder/preprocessor2.js');
+var path = require('path');
 
 module.exports = function (source) {
   // Options must be specified, ignoring request if not.
@@ -24,7 +25,19 @@ module.exports = function (source) {
     return source;
   }
   this.cacheable();
-  var ctx = this.query;
-  source = preprocessor2.preprocessPDFJSCode(ctx, source);
-  return source;
+
+  var filePath = this.resourcePath;
+  var context = this.options.context;
+  var sourcePath = path.relative(context, filePath).split(path.sep).join('/');
+
+  var ctx = Object.create(this.query);
+  ctx.sourceMap = true;
+  ctx.sourceFile = sourcePath;
+
+  var callback = this.callback;
+  var sourceAndMap = preprocessor2.preprocessPDFJSCode(ctx, source);
+  var map = sourceAndMap.map.toJSON();
+  // escodegen does not embed source -- setting map's sourcesContent.
+  map.sourcesContent = [source];
+  callback(null, sourceAndMap.code, map);
 };
diff --git a/gulpfile.js b/gulpfile.js
index 9371002e0..b47fb03bc 100644
--- a/gulpfile.js
+++ b/gulpfile.js
@@ -129,6 +129,8 @@ function createWebpackConfig(defines, output) {
     BUNDLE_BUILD: versionInfo.commit
   });
   var licenseHeader = fs.readFileSync('./src/license_header.js').toString();
+  var enableSourceMaps = !bundleDefines.FIREFOX && !bundleDefines.MOZCENTRAL &&
+                         !bundleDefines.CHROME;
 
   return {
     output: output,
@@ -142,6 +144,7 @@ function createWebpackConfig(defines, output) {
         'pdfjs-web': path.join(__dirname, 'web'),
       }
     },
+    devtool: enableSourceMaps ? 'source-map' : undefined,
     module: {
       loaders: [
         {
@@ -1329,8 +1332,11 @@ gulp.task('dist-repo-prepare', ['dist-pre'], function () {
         .pipe(gulp.dest(DIST_DIR)),
     gulp.src([
       GENERIC_DIR + 'build/pdf.js',
+      GENERIC_DIR + 'build/pdf.js.map',
       GENERIC_DIR + 'build/pdf.worker.js',
+      GENERIC_DIR + 'build/pdf.worker.js.map',
       SINGLE_FILE_DIR + 'build/pdf.combined.js',
+      SINGLE_FILE_DIR + 'build/pdf.combined.js.map',
       SRC_DIR + 'pdf.worker.entry.js',
     ]).pipe(gulp.dest(DIST_DIR + 'build/')),
     gulp.src(MINIFIED_DIR + 'build/pdf.js')