diff --git a/build-system/dep-check-config.js b/build-system/dep-check-config.js
index 79f40e1ef0f7..4478f52e1bac 100644
--- a/build-system/dep-check-config.js
+++ b/build-system/dep-check-config.js
@@ -251,4 +251,11 @@ exports.rules = [
       'src/iframe-helper.js',
     ],
   },
+
+  {
+    mustNotDependOn: [
+      'extensions/amp-ad-network-doubleclick-impl/0.1/amp-ad-network-doubleclick-impl.js',
+      'extensions/amp-ad-network-adsense-impl/0.1/amp-ad-network-adsense-impl.js',
+    ],
+  },
 ];
diff --git a/extensions/amp-ad-network-adsense-impl/0.1/amp-ad-network-adsense-impl.js b/extensions/amp-ad-network-adsense-impl/0.1/amp-ad-network-adsense-impl.js
index a5f61f8b1bf5..07c49b4d2e49 100644
--- a/extensions/amp-ad-network-adsense-impl/0.1/amp-ad-network-adsense-impl.js
+++ b/extensions/amp-ad-network-adsense-impl/0.1/amp-ad-network-adsense-impl.js
@@ -83,6 +83,7 @@ export function resetSharedState() {
   sharedState.reset();
 }
 
+/** @final */
 export class AmpAdNetworkAdsenseImpl extends AmpA4A {
 
   /**
diff --git a/extensions/amp-ad-network-doubleclick-impl/0.1/amp-ad-network-doubleclick-impl.js b/extensions/amp-ad-network-doubleclick-impl/0.1/amp-ad-network-doubleclick-impl.js
index d2084306be45..adbdb080605b 100644
--- a/extensions/amp-ad-network-doubleclick-impl/0.1/amp-ad-network-doubleclick-impl.js
+++ b/extensions/amp-ad-network-doubleclick-impl/0.1/amp-ad-network-doubleclick-impl.js
@@ -279,6 +279,7 @@ function fluidMessageListener_(event) {
   listener.instance.receiveMessageForFluid_(payload);
 }
 
+/** @final */
 export class AmpAdNetworkDoubleclickImpl extends AmpA4A {
 
   /**