diff --git a/addon-sdk/source/lib/sdk/content/sandbox.js b/addon-sdk/source/lib/sdk/content/sandbox.js
index 2545f306c741..08583e4fdb0f 100644
--- a/addon-sdk/source/lib/sdk/content/sandbox.js
+++ b/addon-sdk/source/lib/sdk/content/sandbox.js
@@ -193,7 +193,8 @@ const WorkerSandbox = Class({
     // `addon` in document is equivalent to `self` in content script.
     if (requiresAddonGlobal(worker)) {
       Object.defineProperty(getUnsafeWindow(window), 'addon', {
-          value: content.self
+          value: content.self,
+          configurable: true
         }
       );
     }
diff --git a/addon-sdk/source/lib/sdk/deprecated/traits-worker.js b/addon-sdk/source/lib/sdk/deprecated/traits-worker.js
index 0c16f28d4c20..7ca04e142acd 100644
--- a/addon-sdk/source/lib/sdk/deprecated/traits-worker.js
+++ b/addon-sdk/source/lib/sdk/deprecated/traits-worker.js
@@ -238,7 +238,8 @@ const WorkerSandbox = EventEmitter.compose({
     if (worker._injectInDocument) {
       let win = window.wrappedJSObject ? window.wrappedJSObject : window;
       Object.defineProperty(win, "addon", {
-          value: content.self
+          value: content.self,
+          configurable: true
         }
       );
     }