diff --git a/packages/workbox-webpack-plugin/src/generate-sw.ts b/packages/workbox-webpack-plugin/src/generate-sw.ts
index 5db72cbb3..0f125c82f 100644
--- a/packages/workbox-webpack-plugin/src/generate-sw.ts
+++ b/packages/workbox-webpack-plugin/src/generate-sw.ts
@@ -69,7 +69,7 @@ export interface GenerateSWConfig extends WebpackGenerateSWOptions {
  * @memberof module:workbox-webpack-plugin
  */
 class GenerateSW {
-  private config: GenerateSWConfig;
+  protected config: GenerateSWConfig;
   private alreadyCalled: boolean;
 
   /**
diff --git a/packages/workbox-webpack-plugin/src/inject-manifest.ts b/packages/workbox-webpack-plugin/src/inject-manifest.ts
index 9ef8e07e9..bba10344c 100644
--- a/packages/workbox-webpack-plugin/src/inject-manifest.ts
+++ b/packages/workbox-webpack-plugin/src/inject-manifest.ts
@@ -54,7 +54,7 @@ const {RawSource} = webpack.sources || require('webpack-sources');
  * @memberof module:workbox-webpack-plugin
  */
 class InjectManifest {
-  private config: WebpackInjectManifestOptions;
+  protected config: WebpackInjectManifestOptions;
   private alreadyCalled: boolean;
 
   /**