diff --git a/packages/angular_devkit/build_optimizer/BUILD b/packages/angular_devkit/build_optimizer/BUILD
index 03cc8af56aa7..f4f48cadf65d 100644
--- a/packages/angular_devkit/build_optimizer/BUILD
+++ b/packages/angular_devkit/build_optimizer/BUILD
@@ -26,8 +26,8 @@ ts_library(
     ),
     deps = [
         "@npm//@types/node",
-        "@npm//@types/source-map",
         "@npm//@types/webpack",
+        "@npm//source-map",
         "@npm//typescript",
     ],
 )
@@ -48,7 +48,7 @@ ts_library(
         "//packages/angular_devkit/core",
         "@npm//@types/jasmine",
         "@npm//@types/node",
-        "@npm//@types/source-map",
+        "@npm//source-map",
     ],
     # @external_end
 )
diff --git a/packages/angular_devkit/build_optimizer/package.json b/packages/angular_devkit/build_optimizer/package.json
index 9cb0814b4ea5..ddcd608a1923 100644
--- a/packages/angular_devkit/build_optimizer/package.json
+++ b/packages/angular_devkit/build_optimizer/package.json
@@ -10,7 +10,7 @@
   },
   "dependencies": {
     "loader-utils": "1.2.3",
-    "source-map": "0.5.6",
+    "source-map": "0.7.3",
     "typescript": "3.5.3",
     "webpack-sources": "1.4.1"
   }
diff --git a/packages/angular_devkit/build_optimizer/src/build-optimizer/webpack-loader.ts b/packages/angular_devkit/build_optimizer/src/build-optimizer/webpack-loader.ts
index ec4c138a7900..01d4acbb0f3d 100644
--- a/packages/angular_devkit/build_optimizer/src/build-optimizer/webpack-loader.ts
+++ b/packages/angular_devkit/build_optimizer/src/build-optimizer/webpack-loader.ts
@@ -6,13 +6,12 @@
  * found in the LICENSE file at https://angular.io/license
  */
 import { RawSourceMap, SourceMapConsumer, SourceMapGenerator } from 'source-map';
-import * as webpack from 'webpack';  // tslint:disable-line:no-implicit-dependencies
+import * as webpack from 'webpack'; // tslint:disable-line:no-implicit-dependencies
 
 const loaderUtils = require('loader-utils');
 
 import { buildOptimizer } from './build-optimizer';
 
-
 interface BuildOptimizerLoaderOptions {
   sourceMap: boolean;
 }
@@ -21,17 +20,25 @@ export const buildOptimizerLoaderPath = __filename;
 
 const alwaysProcess = (path: string) =>
   // Always process TS files.
-  path.endsWith('.ts') || path.endsWith('.tsx')
+  path.endsWith('.ts') ||
+  path.endsWith('.tsx') ||
   // Always process factory files.
-  || path.endsWith('.ngfactory.js') || path.endsWith('.ngstyle.js');
-
-export default function buildOptimizerLoader
-  (this: webpack.loader.LoaderContext, content: string, previousSourceMap: RawSourceMap) {
+  path.endsWith('.ngfactory.js') ||
+  path.endsWith('.ngstyle.js');
+
+export default function buildOptimizerLoader(
+  this: webpack.loader.LoaderContext,
+  content: string,
+  previousSourceMap: RawSourceMap,
+) {
   this.cacheable();
+  const callback = this.async();
+  if (!callback) {
+    throw new Error('Async loader support is required.');
+  }
 
-  const skipBuildOptimizer = this._module
-    && this._module.factoryMeta
-    && this._module.factoryMeta.skipBuildOptimizer;
+  const skipBuildOptimizer =
+    this._module && this._module.factoryMeta && this._module.factoryMeta.skipBuildOptimizer;
 
   if (!alwaysProcess(this.resourcePath) && skipBuildOptimizer) {
     // Skip loading processing this file with Build Optimizer if we determined in
@@ -56,9 +63,8 @@ export default function buildOptimizerLoader
     inputFilePath,
     outputFilePath,
     emitSourceMap: options.sourceMap,
-    isSideEffectFree: this._module
-      && this._module.factoryMeta
-      && this._module.factoryMeta.sideEffectFree,
+    isSideEffectFree:
+      this._module && this._module.factoryMeta && this._module.factoryMeta.sideEffectFree,
   });
 
   if (boOutput.emitSkipped || boOutput.content === null) {
@@ -89,10 +95,17 @@ export default function buildOptimizerLoader
       previousSourceMap.file = inputFilePath;
 
       // Chain the sourcemaps.
-      const consumer = new SourceMapConsumer(intermediateSourceMap);
-      const generator = SourceMapGenerator.fromSourceMap(consumer);
-      generator.applySourceMap(new SourceMapConsumer(previousSourceMap));
-      newSourceMap = generator.toJSON();
+      SourceMapConsumer.with(intermediateSourceMap, null, intermediate => {
+        return SourceMapConsumer.with(previousSourceMap, null, previous => {
+          const generator = SourceMapGenerator.fromSourceMap(intermediate);
+          generator.applySourceMap(previous);
+
+          return generator.toJSON();
+        });
+        // tslint:disable-next-line: no-any
+      }).then(map => callback(null, newContent, map as any), error => callback(error));
+
+      return;
     } else {
       // Otherwise just return our generated sourcemap.
       newSourceMap = intermediateSourceMap;
@@ -101,5 +114,5 @@ export default function buildOptimizerLoader
 
   // Webpack typings for previousSourceMap are wrong, they are JSON objects and not strings.
   // tslint:disable-next-line:no-any
-  this.callback(null, newContent, newSourceMap as any);
+  callback(null, newContent, newSourceMap as any);
 }
diff --git a/packages/angular_devkit/core/BUILD b/packages/angular_devkit/core/BUILD
index 8710c3943062..ac754af851a2 100644
--- a/packages/angular_devkit/core/BUILD
+++ b/packages/angular_devkit/core/BUILD
@@ -33,9 +33,9 @@ ts_library(
     deps = [
         "@npm//rxjs",
         "@npm//@types/node",
-        "@npm//@types/source-map",
         "@npm//ajv",
         "@npm//magic-string",
+        "@npm//source-map",
         # @typings: es2015.core
         # @typings: es2015.symbol.wellknown
         # @typings: es2016.array.include
diff --git a/yarn.lock b/yarn.lock
index a22be71b5b4a..faa3cf59b9e0 100644
--- a/yarn.lock
+++ b/yarn.lock
@@ -9719,11 +9719,6 @@ source-map@0.1.x:
   dependencies:
     amdefine ">=0.0.4"
 
-source-map@0.5.6:
-  version "0.5.6"
-  resolved "https://registry.yarnpkg.com/source-map/-/source-map-0.5.6.tgz#75ce38f52bf0733c5a7f0c118d81334a2bb5f412"
-  integrity sha1-dc449SvwczxafwwRjYEzSiu19BI=
-
 source-map@0.7.3, source-map@^0.7.3:
   version "0.7.3"
   resolved "https://registry.yarnpkg.com/source-map/-/source-map-0.7.3.tgz#5302f8169031735226544092e64981f751750383"