diff --git a/.babelrc b/.babelrc
new file mode 100644
index 0000000000..242e95ee03
--- /dev/null
+++ b/.babelrc
@@ -0,0 +1,9 @@
+{
+  "plugins": ["jsdoc-closure"],
+  "parserOpts": {
+    "parser": "recast"
+  },
+  "generatorOpts": {
+    "generator": "recast"
+  }
+}
diff --git a/package.json b/package.json
index 6c5cc011bc..bae113bf4e 100644
--- a/package.json
+++ b/package.json
@@ -15,7 +15,10 @@
     "karma": "karma start test/karma.config.js",
     "serve-examples": "mkdir -p build/examples && webpack --config examples/webpack/config.js --watch & serve build/examples",
     "build-examples": "webpack --config examples/webpack/config.js --env=prod",
-    "build": "webpack --config config/webpack.js"
+    "build-index": "node tasks/generate-index.js",
+    "build": "npm run build-index && webpack --config config/webpack.js",
+    "src-closure": "babel --out-dir build/src-closure src/",
+    "typecheck": "npm run build-index && npm run src-closure && node tasks/typecheck"
   },
   "main": "src/ol/index.js",
   "repository": {
@@ -37,7 +40,9 @@
   },
   "devDependencies": {
     "async": "2.6.0",
+    "babel-cli": "^6.26.0",
     "babel-minify-webpack-plugin": "^0.3.0",
+    "babel-plugin-jsdoc-closure": "^1.0.2",
     "clean-css-cli": "4.1.10",
     "copy-webpack-plugin": "^4.0.1",
     "coveralls": "3.0.0",
@@ -67,6 +72,7 @@
     "nomnom": "1.8.1",
     "pixelmatch": "^4.0.2",
     "proj4": "2.4.4",
+    "recast": "^0.13.0",
     "serve": "^6.0.6",
     "sinon": "4.2.2",
     "url-polyfill": "^1.0.7",
diff --git a/tasks/generate-index.js b/tasks/generate-index.js
index eb3713b26a..dc02268697 100644
--- a/tasks/generate-index.js
+++ b/tasks/generate-index.js
@@ -20,6 +20,10 @@ function getSymbols(callback) {
   });
 }
 
+function getPath(name) {
+  const fullPath = require.resolve(path.resolve('src', name));
+  return './' + path.posix.relative('src/', fullPath);
+}
 
 /**
  * Generate a list of symbol names.
@@ -36,12 +40,12 @@ function addImports(symbols, callback) {
     if (defaultExport.length > 1) {
       const from = defaultExport[0].replace(/^module\:/, './');
       const importName = from.replace(/[.\/]+/g, '$');
-      const defaultImport = `import ${importName} from '${from}.js';`;
+      const defaultImport = `import ${importName} from '${getPath(from)}';`;
       imports[defaultImport] = true;
     } else if (namedExport.length > 1) {
       const from = namedExport[0].replace(/^module\:/, './');
       const importName = from.replace(/[.\/]+/g, '_');
-      const namedImport = `import * as ${importName} from '${from}.js';`;
+      const namedImport = `import * as ${importName} from '${getPath(from)}';`;
       imports[namedImport] = true;
     }
   });
@@ -135,7 +139,7 @@ function main(callback) {
 if (require.main === module) {
   async.waterfall([
     main,
-    fs.outputFile.bind(fs, path.join('src', 'index.js'))
+    fs.outputFile.bind(fs, path.resolve('src', 'index.js'))
   ], function(err) {
     if (err) {
       process.stderr.write(err.message + '\n');
diff --git a/tasks/build-typecheck.js b/tasks/typecheck.js
similarity index 63%
rename from tasks/build-typecheck.js
rename to tasks/typecheck.js
index eee96739e2..9c4632ec41 100644
--- a/tasks/build-typecheck.js
+++ b/tasks/typecheck.js
@@ -2,28 +2,19 @@ const Compiler = require('google-closure-compiler').compiler;
 
 const compiler = new Compiler({
   js: [
-    './src/**.js',
+    './build/src-closure/**.js',
     './node_modules/pbf/package.json', './node_modules/pbf/**.js', './node_modules/ieee754/**.js',
     './node_modules/pixelworks/package.json', './node_modules/pixelworks/**.js',
     './node_modules/rbush/package.json', './node_modules/rbush/**.js', 'node_modules/quickselect/**.js'
   ],
-  entry_point: './src/index.js',
+  entry_point: './build/src-closure/index.js',
   module_resolution: 'NODE',
-  //FIXME Use compilation_level: 'ADVANCED' after we have switched to path types
-  compilation_level: 'SIMPLE',
-  new_type_inf: true,
-  generate_exports: true,
-  export_local_property_definitions: true,
-  output_wrapper: '(function(){%output%})() //# sourceMappingURL=ol.js.map',
-  js_output_file: 'build/ol.js',
-  create_source_map: '%outname%.map',
-  source_map_include_content: true,
-  //FIXME Turn jscomp_error on for * when we have path types everywhere
+  dependency_mode: 'STRICT',
+  process_common_js_modules: true,
+  checks_only: true,
   //FIXME Change newCheckTypes to jscomp_error when we have path types everywhere
   jscomp_warning: ['newCheckTypes'],
   // Options to make dependencies work
-  process_common_js_modules: true,
-  dependency_mode: 'STRICT',
   hide_warnings_for: 'node_modules'
 });