diff --git a/src/SourceMap.js b/src/SourceMap.js
index a55ea4102c7..4908ab6abb9 100644
--- a/src/SourceMap.js
+++ b/src/SourceMap.js
@@ -3,16 +3,37 @@ const lineCounter = require('./utils/lineCounter');
 
 class SourceMap {
   constructor(mappings, sources) {
-    this.mappings = mappings || [];
+    this.mappings = this.purifyMappings(mappings);
     this.sources = sources || {};
     this.lineCount = null;
   }
 
+  purifyMappings(mappings) {
+    if (Array.isArray(mappings)) {
+      return mappings.filter(mapping => {
+        return (
+          mapping &&
+          mapping.source &&
+          mapping.original &&
+          typeof mapping.original.line === 'number' &&
+          mapping.original.line > 0 &&
+          typeof mapping.original.column === 'number' &&
+          mapping.generated &&
+          typeof mapping.generated.line === 'number' &&
+          mapping.generated.line > 0 &&
+          typeof mapping.generated.column === 'number'
+        );
+      });
+    }
+
+    return [];
+  }
+
   async getConsumer(map) {
     if (map instanceof SourceMapConsumer) {
       return map;
     }
-
+    map = typeof map === 'string' ? JSON.parse(map) : map;
     return await new SourceMapConsumer(map);
   }
 
diff --git a/test/integration/sourcemap-typescript-nested/index.ts b/test/integration/sourcemap-typescript-nested/index.ts
new file mode 100644
index 00000000000..5c950cb0369
--- /dev/null
+++ b/test/integration/sourcemap-typescript-nested/index.ts
@@ -0,0 +1,5 @@
+import { local } from './local';
+
+export function env() {
+  return local;
+}
\ No newline at end of file
diff --git a/test/integration/sourcemap-typescript-nested/local.ts b/test/integration/sourcemap-typescript-nested/local.ts
new file mode 100644
index 00000000000..6386b8a701c
--- /dev/null
+++ b/test/integration/sourcemap-typescript-nested/local.ts
@@ -0,0 +1 @@
+exports.local = process.env.NODE_ENV;
\ No newline at end of file
diff --git a/test/sourcemaps.js b/test/sourcemaps.js
index 0b6c10618d6..0c2a8f82472 100644
--- a/test/sourcemaps.js
+++ b/test/sourcemaps.js
@@ -61,6 +61,35 @@ describe('sourcemaps', function() {
     assert.equal(output.env(), process.env.NODE_ENV);
   });
 
+  it('should create a valid sourcemap as a child of a nested TS bundle', async function() {
+    let b = await bundle(
+      __dirname + '/integration/sourcemap-typescript-nested/index.ts'
+    );
+
+    assertBundleTree(b, {
+      name: 'index.js',
+      assets: ['index.ts', 'local.ts'],
+      childBundles: [
+        {
+          name: 'index.map',
+          type: 'map'
+        }
+      ]
+    });
+
+    let raw = fs
+      .readFileSync(path.join(__dirname, '/dist/index.js'))
+      .toString();
+    let map = fs
+      .readFileSync(path.join(__dirname, '/dist/index.map'))
+      .toString();
+    mapValidator(raw, map);
+
+    let output = run(b);
+    assert.equal(typeof output.env, 'function');
+    assert.equal(output.env(), process.env.NODE_ENV);
+  });
+
   it('should create a valid sourcemap for a js file with requires', async function() {
     let b = await bundle(__dirname + '/integration/sourcemap-nested/index.js');