diff --git a/modules/@angular/compiler-cli/src/extractor.ts b/modules/@angular/compiler-cli/src/extractor.ts
index b51e1ce0d7..a6f27fb9e2 100644
--- a/modules/@angular/compiler-cli/src/extractor.ts
+++ b/modules/@angular/compiler-cli/src/extractor.ts
@@ -31,10 +31,7 @@ export class Extractor {
     // Checks the format and returns the extension
     const ext = this.getExtension(formatName);
 
-    const files = this.program.getSourceFiles().map(
-        sf => this.ngCompilerHost.getCanonicalFileName(sf.fileName));
-
-    const promiseBundle = this.ngExtractor.extract(files);
+    const promiseBundle = this.extractBundle();
 
     return promiseBundle.then(bundle => {
       const content = this.serialize(bundle, ext);
@@ -43,6 +40,13 @@ export class Extractor {
     });
   }
 
+  extractBundle(): Promise<compiler.MessageBundle> {
+    const files = this.program.getSourceFiles().map(
+        sf => this.ngCompilerHost.getCanonicalFileName(sf.fileName));
+
+    return this.ngExtractor.extract(files);
+  }
+
   serialize(bundle: compiler.MessageBundle, ext: string): string {
     let serializer: compiler.Serializer;