diff --git a/src/assets/JSAsset.js b/src/assets/JSAsset.js
index c9e6c1422b3..3e089da0924 100644
--- a/src/assets/JSAsset.js
+++ b/src/assets/JSAsset.js
@@ -119,23 +119,57 @@ class JSAsset extends Asset {
       let dataURLMatch = url.match(DATA_URL_RE);
 
       try {
-        let json;
+        let json, filename;
         if (dataURLMatch) {
+          filename = this.name;
           json = new Buffer(dataURLMatch[1], 'base64').toString();
         } else {
-          json = await fs.readFile(
-            path.join(path.dirname(this.name), url),
-            'utf8'
-          );
+          filename = path.join(path.dirname(this.name), url);
+          json = await fs.readFile(filename, 'utf8');
+
+          // Add as a dep so we watch the source map for changes.
+          this.addDependency(filename, {includedInParent: true});
         }
 
         this.sourceMap = JSON.parse(json);
 
-        // Add as a dep so we watch the source map for changes.
-        this.addDependency(match[1], {includedInParent: true});
+        // Attempt to read missing source contents
+        if (!this.sourceMap.sourcesContent) {
+          this.sourceMap.sourcesContent = [];
+        }
+
+        let missingSources = this.sourceMap.sources.slice(
+          this.sourceMap.sourcesContent.length
+        );
+        if (missingSources.length) {
+          let contents = await Promise.all(
+            missingSources.map(async source => {
+              try {
+                let sourceFile = path.join(
+                  path.dirname(filename),
+                  this.sourceMap.sourceRoot || '',
+                  source
+                );
+                let result = await fs.readFile(sourceFile, 'utf8');
+                this.addDependency(sourceFile, {includedInParent: true});
+                return result;
+              } catch (err) {
+                logger.warn(
+                  `Could not load source file "${source}" in source map of "${
+                    this.relativeName
+                  }".`
+                );
+              }
+            })
+          );
+
+          this.sourceMap.sourcesContent = this.sourceMap.sourcesContent.concat(
+            contents
+          );
+        }
       } catch (e) {
         logger.warn(
-          `Could not load existing sourcemap of ${this.relativeName}.`
+          `Could not load existing sourcemap of "${this.relativeName}".`
         );
       }
     }
diff --git a/test/integration/sourcemap-external-contents/index.js b/test/integration/sourcemap-external-contents/index.js
new file mode 100644
index 00000000000..66b67d1dbc5
--- /dev/null
+++ b/test/integration/sourcemap-external-contents/index.js
@@ -0,0 +1,5 @@
+const sum = require('./sum');
+
+module.exports = function() {
+  return sum(1, 2);
+}
\ No newline at end of file
diff --git a/test/integration/sourcemap-external-contents/sum.coffee b/test/integration/sourcemap-external-contents/sum.coffee
new file mode 100644
index 00000000000..e84213f385f
--- /dev/null
+++ b/test/integration/sourcemap-external-contents/sum.coffee
@@ -0,0 +1 @@
+module.exports = (a, b) => a + b
diff --git a/test/integration/sourcemap-external-contents/sum.js b/test/integration/sourcemap-external-contents/sum.js
new file mode 100644
index 00000000000..00d08409ec2
--- /dev/null
+++ b/test/integration/sourcemap-external-contents/sum.js
@@ -0,0 +1,11 @@
+// Generated by CoffeeScript 1.12.6
+(function() {
+  module.exports = (function(_this) {
+    return function(a, b) {
+      return a + b;
+    };
+  })(this);
+
+}).call(this);
+
+//# sourceMappingURL=sum.map
diff --git a/test/integration/sourcemap-external-contents/sum.map b/test/integration/sourcemap-external-contents/sum.map
new file mode 100644
index 00000000000..87b0481c875
--- /dev/null
+++ b/test/integration/sourcemap-external-contents/sum.map
@@ -0,0 +1,10 @@
+{
+  "version": 3,
+  "file": "sum.js",
+  "sourceRoot": "",
+  "sources": [
+    "sum.coffee"
+  ],
+  "names": [],
+  "mappings": ";AAAA;EAAA,MAAM,CAAC,OAAP,GAAiB,CAAA,SAAA,KAAA;WAAA,SAAC,CAAD,EAAI,CAAJ;aAAU,CAAA,GAAI;IAAd;EAAA,CAAA,CAAA,CAAA,IAAA;AAAjB"
+}
diff --git a/test/sourcemaps.js b/test/sourcemaps.js
index c8bb5f51a88..be8b1223ad0 100644
--- a/test/sourcemaps.js
+++ b/test/sourcemaps.js
@@ -274,4 +274,40 @@ describe('sourcemaps', function() {
     );
     mapValidator(jsOutput, map);
   });
+
+  it('should load referenced contents of sourcemaps', async function() {
+    let b = await bundle(
+      __dirname + '/integration/sourcemap-external-contents/index.js'
+    );
+
+    assertBundleTree(b, {
+      name: 'index.js',
+      assets: ['index.js', 'sum.js'],
+      childBundles: [
+        {
+          type: 'map'
+        }
+      ]
+    });
+
+    let jsOutput = await fs.readFile(b.name, 'utf8');
+
+    let sourcemapReference = path.join(
+      __dirname,
+      '/dist/',
+      jsOutput.substring(jsOutput.lastIndexOf('//# sourceMappingURL') + 22)
+    );
+
+    assert(
+      await fs.exists(path.join(sourcemapReference)),
+      'referenced sourcemap should exist'
+    );
+
+    let map = await fs.readFile(path.join(sourcemapReference), 'utf8');
+    assert(
+      map.indexOf('module.exports = (a, b) => a + b') > -1,
+      'Sourcemap should contain the existing sourcemap'
+    );
+    mapValidator(jsOutput, map);
+  });
 });