--- a/addon-sdk/source/app-extension/bootstrap.js
+++ b/addon-sdk/source/app-extension/bootstrap.js
@@ -293,21 +293,18 @@ function loadSandbox(uri) {
       CC: bind(CC, Components), components: Components,
       ChromeWorker: ChromeWorker });
   };
   scriptLoader.loadSubScript(uri, sandbox, 'UTF-8');
   return sandbox;
 }
 
 function unloadSandbox(sandbox) {
-  if ("nukeSandbox" in Cu) {
-    try {
-      Cu.nukeSandbox(sandbox);
-    } catch (e) {}
-  }
+  if (Cu.getClassName(sandbox, true) == "Sandbox")
+    Cu.nukeSandbox(sandbox);
 }
 
 function setTimeout(callback, delay) {
   let timer = Cc["@mozilla.org/timer;1"].createInstance(Ci.nsITimer);
   timer.initWithCallback({ notify: callback }, delay,
                          Ci.nsITimer.TYPE_ONE_SHOT);
   return timer;
 }

--- a/addon-sdk/source/test/addons/l10n-properties/app-extension/bootstrap.js
+++ b/addon-sdk/source/test/addons/l10n-properties/app-extension/bootstrap.js
@@ -275,17 +275,17 @@ function loadSandbox(uri) {
       CC: bind(CC, Components), components: Components,
       ChromeWorker: ChromeWorker });
   };
   scriptLoader.loadSubScript(uri, sandbox, 'UTF-8');
   return sandbox;
 }
 
 function unloadSandbox(sandbox) {
-  if ("nukeSandbox" in Cu)
+  if (Cu.getClassName(sandbox, true) == "Sandbox")
     Cu.nukeSandbox(sandbox);
 }
 
 function setTimeout(callback, delay) {
   let timer = Cc["@mozilla.org/timer;1"].createInstance(Ci.nsITimer);
   timer.initWithCallback({ notify: callback }, delay,
                          Ci.nsITimer.TYPE_ONE_SHOT);
   return timer;

--- a/addon-sdk/source/test/addons/simple-prefs-regression/app-extension/bootstrap.js
+++ b/addon-sdk/source/test/addons/simple-prefs-regression/app-extension/bootstrap.js
@@ -275,17 +275,17 @@ function loadSandbox(uri) {
       CC: bind(CC, Components), components: Components,
       ChromeWorker: ChromeWorker });
   };
   scriptLoader.loadSubScript(uri, sandbox, 'UTF-8');
   return sandbox;
 }
 
 function unloadSandbox(sandbox) {
-  if ("nukeSandbox" in Cu)
+  if (Cu.getClassName(sandbox, true) == "Sandbox")
     Cu.nukeSandbox(sandbox);
 }
 
 function setTimeout(callback, delay) {
   let timer = Cc["@mozilla.org/timer;1"].createInstance(Ci.nsITimer);
   timer.initWithCallback({ notify: callback }, delay,
                          Ci.nsITimer.TYPE_ONE_SHOT);
   return timer;