diff --git a/package.json b/package.json
index d7ccf56..76ee2e6 100644
--- a/package.json
+++ b/package.json
@@ -15,6 +15,7 @@
     "posttest-coverage": "remap-istanbul -i coverage/coverage-final.json -o coverage/coverage-remapped.json -b dist && remap-istanbul -i coverage/coverage-final.json -o coverage/coverage-remapped.lcov -t lcovonly -b dist && remap-istanbul -i coverage/coverage-final.json -o coverage/coverage-remapped -t html -b dist",
     "ci": "npm run test-coverage && codecov < coverage/coverage-remapped.lcov",
     "build": "git rev-parse HEAD > .commithash && rollup -c",
+    "watch": "rollup -c -w",
     "build:cli": "rollup -c rollup.config.cli.js",
     "build:browser": "git rev-parse HEAD > .commithash && rollup -c rollup.config.browser.js -o dist/rollup.browser.js",
     "prepublish": "npm run lint && npm test && npm run build:browser",
@@ -49,7 +50,7 @@
     "eslint": "^2.13.0",
     "estree-walker": "^0.2.1",
     "istanbul": "^0.4.3",
-    "magic-string": "^0.15.1",
+    "magic-string": "^0.15.2",
     "minimist": "^1.2.0",
     "mocha": "^2.5.3",
     "remap-istanbul": "^0.6.4",
diff --git a/test/sourcemaps/reified-namespace/_config.js b/test/sourcemaps/reified-namespace/_config.js
new file mode 100644
index 0000000..8870098
--- /dev/null
+++ b/test/sourcemaps/reified-namespace/_config.js
@@ -0,0 +1,22 @@
+const fs = require( 'fs' );
+const path = require( 'path' );
+const assert = require( 'assert' );
+const getLocation = require( '../../utils/getLocation' );
+const SourceMapConsumer = require( 'source-map' ).SourceMapConsumer;
+
+module.exports = {
+	description: 'generates correct sourcemap with reified namespace (#668)',
+	test: ( code, map ) => {
+		const smc = new SourceMapConsumer( map );
+
+		const main = fs.readFileSync( path.join( __dirname, 'main.js' ), 'utf-8' );
+		const generatedLoc = getLocation( code, 'deepEqual' );
+
+		const actual = smc.originalPositionFor( generatedLoc );
+		const expected = getLocation( main, 'deepEqual' );
+
+		assert.equal( actual.line, expected.line );
+		assert.equal( actual.column, expected.column );
+		assert.equal( actual.source, '../main.js' );
+	}
+};
diff --git a/test/sourcemaps/reified-namespace/foo.js b/test/sourcemaps/reified-namespace/foo.js
new file mode 100644
index 0000000..ab0c7db
--- /dev/null
+++ b/test/sourcemaps/reified-namespace/foo.js
@@ -0,0 +1 @@
+export var bar = 42;
diff --git a/test/sourcemaps/reified-namespace/main.js b/test/sourcemaps/reified-namespace/main.js
new file mode 100644
index 0000000..565c1eb
--- /dev/null
+++ b/test/sourcemaps/reified-namespace/main.js
@@ -0,0 +1,3 @@
+import * as foo from './foo.js';
+
+assert.deepEqual( foo, { bar: 42 });
diff --git a/test/utils/getLocation.js b/test/utils/getLocation.js
index 4993997..b92d38b 100644
--- a/test/utils/getLocation.js
+++ b/test/utils/getLocation.js
@@ -1,10 +1,12 @@
-module.exports = function getLocation ( source, charIndex ) {
+module.exports = function getLocation ( source, search ) {
 	var lines = source.split( '\n' );
 	var len = lines.length;
 
 	var lineStart = 0;
 	var i;
 
+	const charIndex = typeof search === 'number' ? search : source.indexOf( search );
+
 	for ( i = 0; i < len; i += 1 ) {
 		var line = lines[i];
 		var lineEnd =  lineStart + line.length + 1; // +1 for newline