diff --git a/chrome/content/zotero/xpcom/translation/translate.js b/chrome/content/zotero/xpcom/translation/translate.js
index 7a5ada378..268870191 100644
--- a/chrome/content/zotero/xpcom/translation/translate.js
+++ b/chrome/content/zotero/xpcom/translation/translate.js
@@ -1157,7 +1157,7 @@ Zotero.Translate.Base.prototype = {
 	 */
 	"_loadTranslator":function(translator, callback) {
 		var sandboxLocation = this._getSandboxLocation();
-		if(!this._sandboxLocation || sandboxLocation != this._sandboxLocation) {
+		if(!this._sandboxLocation || sandboxLocation !== this._sandboxLocation) {
 			this._sandboxLocation = sandboxLocation;
 			this._generateSandbox();
 		}
diff --git a/chrome/content/zotero/xpcom/translation/translate_firefox.js b/chrome/content/zotero/xpcom/translation/translate_firefox.js
index a7892ca62..61d583ba9 100644
--- a/chrome/content/zotero/xpcom/translation/translate_firefox.js
+++ b/chrome/content/zotero/xpcom/translation/translate_firefox.js
@@ -129,7 +129,11 @@ Zotero.Translate.SandboxManager.prototype = {
 	 * Evaluates code in the sandbox
 	 */
 	"eval":function(code, exported, path) {
-		Components.utils.evalInSandbox(code, this.sandbox, "1.8", path, 1);
+		if(Zotero.isFx4) {
+			Components.utils.evalInSandbox(code, this.sandbox, "1.8", path, 1);
+		} else {
+			Components.utils.evalInSandbox(code, this.sandbox);
+		}
 	},
 	
 	/**
@@ -147,7 +151,6 @@ Zotero.Translate.SandboxManager.prototype = {
 			let localKey = key;
 			if(newExposedProps) newExposedProps[localKey] = "r";
 			
-			// magical XPCSafeJSObjectWrappers for sandbox
 			var type = typeof object[localKey];
 			var isFunction = type === "function";
 			var isObject = typeof object[localKey] === "object";
@@ -171,9 +174,7 @@ Zotero.Translate.SandboxManager.prototype = {
 							}
 							
 							for(var i=0, nArgs=arguments.length; i<nArgs; i++) {
-								args[i+offset] = (((typeof arguments[i] === "object" && arguments[i] !== null)
-									|| typeof arguments[i] === "function") 
-									? new XPCSafeJSObjectWrapper(arguments[i]) : arguments[i]);
+								args[i+offset] = arguments[i];
 							}
 							
 							return object[localKey].apply(object, args);
diff --git a/chrome/content/zotero/xpcom/zotero.js b/chrome/content/zotero/xpcom/zotero.js
index a9fa79c2f..212c6cb8b 100644
--- a/chrome/content/zotero/xpcom/zotero.js
+++ b/chrome/content/zotero/xpcom/zotero.js
@@ -37,17 +37,6 @@ const ZOTERO_CONFIG = {
 	PREF_BRANCH: 'extensions.zotero.'
 };
 
-const ZOTERO_METAREGEXP = /[-[\]{}()*+?.\\^$|,#\s]/g;
-
-// Fx4.0b8+ use implicit SJOWs and get rid of explicit XPCSafeJSObjectWrapper constructor
-// Ugly hack to get around this until we can just kill the XPCSafeJSObjectWrapper calls (when we
-// drop Fx3.6 support)
-try {
-	XPCSafeJSObjectWrapper;
-} catch(e) {
-	eval("var XPCSafeJSObjectWrapper = function(arg) { return arg }");
-}
-
 // Load AddonManager for Firefox 4
 var appInfo = Components.classes["@mozilla.org/xre/app-info;1"].
                          getService(Components.interfaces.nsIXULAppInfo);
@@ -392,7 +381,11 @@ if(appInfo.platformVersion[0] >= 2) {
 						
 						// evaluate
 						Components.utils.evalInSandbox(prefsJs, sandbox);
-						var prefs = new XPCSafeJSObjectWrapper(sandbox.prefs);
+						if(Zotero.isFx4) {
+							var prefs = sandbox.prefs;
+						} else {
+							var prefs = new XPCSafeJSObjectWrapper(sandbox.prefs);
+						}
 						for(var key in prefs) {
 							if(key.substr(0, ZOTERO_CONFIG.PREF_BRANCH.length) === ZOTERO_CONFIG.PREF_BRANCH
 									&& key !== "extensions.zotero.firstRun2") {