diff --git a/chrome/content/zotero/bindings/itembox.xml b/chrome/content/zotero/bindings/itembox.xml
index 750476f1f9..11ffeacd0c 100644
--- a/chrome/content/zotero/bindings/itembox.xml
+++ b/chrome/content/zotero/bindings/itembox.xml
@@ -1729,7 +1729,7 @@
 							this._addCreatorRow = false;
 							
 							//Filter out bad names
-							var nameArray = [tempName for each(tempName in rawNameArray) if(tempName)];
+							var nameArray = rawNameArray.filter(name => name);
 							
 							//If not adding names at the end of the creator list, make new creator 
 							//entries and then shift down existing creators.
diff --git a/chrome/content/zotero/fileInterface.js b/chrome/content/zotero/fileInterface.js
index f9074ab249..a48ac8450e 100644
--- a/chrome/content/zotero/fileInterface.js
+++ b/chrome/content/zotero/fileInterface.js
@@ -328,7 +328,7 @@ var Zotero_File_Interface = new function() {
 			translation.setHandler("done", function(obj, worked) {
 				// add items to import collection
 				if(importCollection) {
-					importCollection.addItems([item.id for each(item in obj.newItems)]);
+					importCollection.addItems(obj.newItems.map(item => item.id));
 				}
 				
 				Zotero.DB.commitTransaction();
@@ -467,7 +467,10 @@ var Zotero_File_Interface = new function() {
 							   getService(Components.interfaces.nsIClipboard);
 		
 		var style = Zotero.Styles.get(style).getCiteProc(locale);
-		var citation = {"citationItems":[{id:item.id} for each(item in items)], properties:{}};
+		var citation = {
+			citationItems: items.map(item => ({ id: item.id })),
+			properties: {}
+		};
 		
 		// add HTML
 		var bibliography = style.previewCitationCluster(citation, [], [], "html");
diff --git a/chrome/content/zotero/integration/editBibliographyDialog.js b/chrome/content/zotero/integration/editBibliographyDialog.js
index f9663dde2d..067bedcbe8 100644
--- a/chrome/content/zotero/integration/editBibliographyDialog.js
+++ b/chrome/content/zotero/integration/editBibliographyDialog.js
@@ -99,7 +99,7 @@ var Zotero_Bibliography_Dialog = new function () {
 			_addButton.disabled = true;
 			_removeButton.disabled = false;
 			_updateRevertButtonStatus();
-			[_itemList.toggleItemSelection(item) for each(item in itemsToSelect)];
+			itemsToSelect.forEach(item => _itemList.toggleItemSelection(item));
 			_itemList.ensureIndexIsVisible(itemsToSelect[0]);
 		}
 		_suppressAllSelectEvents = false;
diff --git a/chrome/content/zotero/integration/quickFormat.js b/chrome/content/zotero/integration/quickFormat.js
index 95f24e1761..abecb23309 100644
--- a/chrome/content/zotero/integration/quickFormat.js
+++ b/chrome/content/zotero/integration/quickFormat.js
@@ -303,9 +303,13 @@ var Zotero_QuickFormat = new function () {
 						citedItemsMatchingSearch = [];
 					for(var i=0, iCount=citedItems.length; i<iCount; i++) {
 						// Generate a string to search for each item
-						var item = citedItems[i],
-							itemStr = [creator.ref.firstName+" "+creator.ref.lastName for (creator of item.getCreators())];
-						itemStr = itemStr.concat([item.getField("title"), item.getField("date", true, true).substr(0, 4)]).join(" ");
+						let item = citedItems[i];
+						let itemStr = item.getCreators()
+							.map(creator => {
+								creator.ref.firstName + " " + creator.ref.lastName
+							})
+							.concat([item.getField("title"), item.getField("date", true, true).substr(0, 4)])
+							.join(" ");
 						
 						// See if words match
 						for(var j=0, jCount=splits.length; j<jCount; j++) {
diff --git a/chrome/content/zotero/locateManager.xul b/chrome/content/zotero/locateManager.xul
index fa4e35b179..6dd9766f02 100644
--- a/chrome/content/zotero/locateManager.xul
+++ b/chrome/content/zotero/locateManager.xul
@@ -231,7 +231,7 @@ To add a new preference:
 				hidden = false;
 			}
 			
-			[engine.hidden = hidden for each(engine in Zotero.LocateManager.getEngines())];
+			Zotero.LocateManager.getEngines().forEach(engine => engine.hidden = hidden);
 
 			refreshLocateEnginesList();
 		}
diff --git a/chrome/content/zotero/rtfScan.js b/chrome/content/zotero/rtfScan.js
index 9a44c8cd8e..ffa9cc7884 100644
--- a/chrome/content/zotero/rtfScan.js
+++ b/chrome/content/zotero/rtfScan.js
@@ -528,7 +528,7 @@ var Zotero_RTFScan = new function() {
 		}
 		Zotero.debug(cslCitations);
 		
-		itemIDs = [itemID for(itemID in itemIDs)];
+		itemIDs = Object.keys(itemIDs);
 		Zotero.debug(itemIDs);
 		
 		// prepare the list of rendered citations
diff --git a/chrome/content/zotero/tools/cslpreview.js b/chrome/content/zotero/tools/cslpreview.js
index 8ff06009db..b0e841a97b 100644
--- a/chrome/content/zotero/tools/cslpreview.js
+++ b/chrome/content/zotero/tools/cslpreview.js
@@ -95,13 +95,17 @@ var Zotero_CSL_Preview = new function() {
 		
 		// Generate multiple citations
 		var citations = styleEngine.previewCitationCluster(
-		{"citationItems":[{"id":item.id} for each(item in items)], "properties":{}},
-		[], [], "html");
+			{
+				citationItems: items.map(item => ({ id: item.id })),
+				properties: {}
+			},
+			[], [], "html"
+		);
 		
 		// Generate bibliography
 		var bibliography = '';
 		if(style.hasBibliography) {
-			styleEngine.updateItems([item.id for each(item in items)]);
+			styleEngine.updateItems(items.map(item => item.id));
 			bibliography = Zotero.Cite.makeFormattedBibliography(styleEngine, "html");
 		}
 		
diff --git a/chrome/content/zotero/xpcom/cite.js b/chrome/content/zotero/xpcom/cite.js
index 183101e3ed..467164b951 100644
--- a/chrome/content/zotero/xpcom/cite.js
+++ b/chrome/content/zotero/xpcom/cite.js
@@ -73,7 +73,7 @@ Zotero.Cite = {
 	 */
 	"makeFormattedBibliographyOrCitationList":function(cslEngine, items, format, asCitationList) {
 		cslEngine.setOutputFormat(format);
-		cslEngine.updateItems([item.id for each(item in items)]);
+		cslEngine.updateItems(items.map(item => item.id));
 		 		
 		if(!asCitationList) {
 			var bibliography = Zotero.Cite.makeFormattedBibliography(cslEngine, format);
@@ -297,7 +297,7 @@ Zotero.Cite = {
 		var slashIndex;
 		
 		if(id instanceof Array) {
-			return [Zotero.Cite.getItem(anId) for each(anId in id)];
+			return id.map(anId => Zotero.Cite.getItem(anId));
 		} else if(typeof id === "string" && (slashIndex = id.indexOf("/")) !== -1) {		
 			var sessionID = id.substr(0, slashIndex),
 				session = Zotero.Integration.sessions[sessionID],
diff --git a/chrome/content/zotero/xpcom/data/tag.js b/chrome/content/zotero/xpcom/data/tag.js
index b2133a2ee0..b91fac9f1a 100644
--- a/chrome/content/zotero/xpcom/data/tag.js
+++ b/chrome/content/zotero/xpcom/data/tag.js
@@ -224,7 +224,7 @@ Zotero.Tag.prototype.getLinkedItems = function (asIDs) {
 	}
 	
 	// Return Zotero.Item objects
-	return [item for each(item in this._linkedItems)];
+	return Object.keys(this._linkedItems).map(id => this._linkedItems[id]);
 }
 
 
diff --git a/chrome/content/zotero/xpcom/fulltext.js b/chrome/content/zotero/xpcom/fulltext.js
index d5bc5645e8..bc9df96e99 100644
--- a/chrome/content/zotero/xpcom/fulltext.js
+++ b/chrome/content/zotero/xpcom/fulltext.js
@@ -446,7 +446,7 @@ Zotero.Fulltext = new function(){
 		Zotero.DB.query("DELETE FROM indexing.fulltextWords");
 		while (words.length > 0) {
 			chunk = words.splice(0, 100);
-			Zotero.DB.query('INSERT INTO indexing.fulltextWords (word) ' + ['SELECT ?' for (word of chunk)].join(' UNION '), chunk);
+			Zotero.DB.query('INSERT INTO indexing.fulltextWords (word) ' + chunk.map(x => 'SELECT ?').join(' UNION '), chunk);
 		}
 		Zotero.DB.query('INSERT OR IGNORE INTO fulltextWords (word) SELECT word FROM indexing.fulltextWords');
 		Zotero.DB.query('DELETE FROM fulltextItemWords WHERE itemID = ?', [itemID]);
diff --git a/chrome/content/zotero/xpcom/integration.js b/chrome/content/zotero/xpcom/integration.js
index 106ab228da..ea86d72932 100644
--- a/chrome/content/zotero/xpcom/integration.js
+++ b/chrome/content/zotero/xpcom/integration.js
@@ -1554,7 +1554,7 @@ Zotero.Integration.Fields.prototype.updateDocument = function(forceCitations, fo
 Zotero.Integration.Fields.prototype._updateDocument = function(forceCitations, forceBibliography,
 		ignoreCitationChanges) {
 	if(this.progressCallback) {
-		var nFieldUpdates = [i for(i in this._session.updateIndices)].length;
+		var nFieldUpdates = Object.keys(this._session.updateIndices).length;
 		if(this._session.bibliographyHasChanged || forceBibliography) {
 			nFieldUpdates += this._bibliographyFields.length*5;
 		}
@@ -1989,11 +1989,13 @@ Zotero.Integration.CitationEditInterface.prototype = {
 	 */
 	"_getItems":function() {
 		var citationsByItemID = this._session.citationsByItemID;
-		var ids = [itemID for(itemID in citationsByItemID)
-			if(citationsByItemID[itemID] && citationsByItemID[itemID].length
+		var ids = Object.keys(citationsByItemID).filter(itemID => {
+			return citationsByItemID[itemID]
+				&& citationsByItemID[itemID].length
 				// Exclude the present item
 				&& (citationsByItemID[itemID].length > 1
-					|| citationsByItemID[itemID][0].properties.zoteroIndex !== this._fieldIndex))];
+					|| citationsByItemID[itemID][0].properties.zoteroIndex !== this._fieldIndex);
+		});
 		
 		// Sort all previously cited items at top, and all items cited later at bottom
 		var fieldIndex = this._fieldIndex;
@@ -2565,7 +2567,7 @@ Zotero.Integration.Session.prototype.getBibliography = function() {
 Zotero.Integration.Session.prototype.updateUncitedItems = function() {
 	// There appears to be a bug somewhere here.
 	if(Zotero.Debug.enabled) Zotero.debug("Integration: style.updateUncitedItems("+this.uncitedItems.toSource()+")");
-	this.style.updateUncitedItems([parseInt(i) for(i in this.uncitedItems)]);
+	this.style.updateUncitedItems(Object.keys(this.uncitedItems).map(i => parseInt(i)));
 }
 
 /**
@@ -2662,9 +2664,9 @@ Zotero.Integration.Session.prototype._updateCitations = function() {
 	
 	if(Zotero.Debug.enabled) {
 		Zotero.debug("Integration: Indices of new citations");
-		Zotero.debug([key for(key in this.newIndices)]);
+		Zotero.debug(Object.keys(this.newIndices));
 		Zotero.debug("Integration: Indices of updated citations");
-		Zotero.debug([key for(key in this.updateIndices)]);
+		Zotero.debug(Object.keys(this.updateIndices));
 	}
 	
 	
@@ -2818,8 +2820,9 @@ Zotero.Integration.Session.prototype.getBibliographyData = function() {
 	}
 	
 	// look for custom bibliography entries
-	bibliographyData.custom = [[this.uriMap.getURIsForItemID(id), this.customBibliographyText[id]]
-		for(id in this.customBibliographyText)];
+	bibliographyData.custom = Object.keys(this.customBibliographyText)
+		.map(id => [this.uriMap.getURIsForItemID(id), this.customBibliographyText[id]]);
+	
 	
 	if(bibliographyData.uncited || bibliographyData.custom) {
 		return JSON.stringify(bibliographyData);
diff --git a/chrome/content/zotero/xpcom/itemTreeView.js b/chrome/content/zotero/xpcom/itemTreeView.js
index 715b4efceb..217f2a9dcb 100644
--- a/chrome/content/zotero/xpcom/itemTreeView.js
+++ b/chrome/content/zotero/xpcom/itemTreeView.js
@@ -2428,7 +2428,7 @@ Zotero.ItemTreeView.prototype.onColumnPickerShowing = function (event) {
 		moreMenuPopup.setAttribute('anonid', id + '-popup');
 		
 		let treecols = menupopup.parentNode.parentNode;
-		let subs = [x.getAttribute('label') for (x of treecols.getElementsByAttribute('submenu', 'true'))];
+		let subs = treecols.getElementsByAttribute('submenu', 'true').map(x => x.getAttribute('label'));
 		
 		var moreItems = [];
 		
diff --git a/chrome/content/zotero/xpcom/locateManager.js b/chrome/content/zotero/xpcom/locateManager.js
index cefad9238a..9d603fb04a 100644
--- a/chrome/content/zotero/xpcom/locateManager.js
+++ b/chrome/content/zotero/xpcom/locateManager.js
@@ -42,8 +42,8 @@ Zotero.LocateManager = new function() {
 		_jsonFile = _getLocateFile();
 		
 		if(_jsonFile.exists()) {
-			_locateEngines = [new LocateEngine(engine)
-				for each(engine in JSON.parse(Zotero.File.getContents(_jsonFile)))];
+			_locateEngines = JSON.parse(Zotero.File.getContents(_jsonFile))
+				.map(engine => new LocateEngine(engine));
 		} else {
 			this.restoreDefaultEngines();
 		}
@@ -67,8 +67,10 @@ Zotero.LocateManager = new function() {
 	/**
 	 * Gets all default search engines (not currently used)
 	 */
-	this.getDefaultEngines = function() [new LocateEngine(engine)
-				for each(engine in JSON.parse(Zotero.File.getContentsFromURL(_getDefaultFile())))];
+	this.getDefaultEngines = function () {
+		return JSON.parse(Zotero.File.getContentsFromURL(_getDefaultFile()))
+			.map(engine => new LocateEngine(engine));
+	}
 	
 	/**
 	 * Returns an array of all search engines
@@ -78,7 +80,9 @@ Zotero.LocateManager = new function() {
 	/**
 	 * Returns an array of all search engines visible that should be visible in the dropdown
 	 */
-	this.getVisibleEngines = function() [engine for each(engine in _locateEngines) if(!engine.hidden)];
+	this.getVisibleEngines = function () {
+		return _locateEngines.filter(engine => !engine.hidden);
+	}
 	
 	/**
 	 * Returns an engine with a specific name
@@ -285,12 +289,12 @@ Zotero.LocateManager = new function() {
 				return false;
 			}
 			
-			return [encodeURIComponent(val) for each(val in itemOpenURL["rft."+param])];
+			return itemOpenURL["rft."+param].map(val => encodeURIComponent(val));
 		} else if(ns === "info:ofi/fmt:kev:mtx:ctx") {
 			if(!OPENURL_CONTEXT_MAPPINGS[param] || !itemOpenURL[OPENURL_CONTEXT_MAPPINGS[param]]) {
 				return false;
 			}
-			return [encodeURIComponent(val) for each(val in itemOpenURL[OPENURL_CONTEXT_MAPPINGS[param]])];
+			return itemOpenURL[OPENURL_CONTEXT_MAPPINGS[param]].map(val => encodeURIComponent(val));
 		} else if(ns === "http://www.zotero.org/namespaces/openSearch#") {
 			if(param === "openURL") {
 				var ctx = Zotero.OpenURL.createContextObject(item, "1.0");
@@ -457,7 +461,10 @@ Zotero.LocateManager = new function() {
 				} else {
 					var result = _lookupParam(item, itemAsOpenURL, me, m[1], m[2]);
 					if(result) {
-						paramsToAdd = paramsToAdd.concat([encodeURIComponent(param)+"="+encodeURIComponent(val) for(val in result)]);
+						paramsToAdd = paramsToAdd.concat(
+							result.map(val =>
+								encodeURIComponent(param) + "=" + encodeURIComponent(val))
+						);
 					} else if(m[3]) {	// if no param and it wasn't optional, return
 						return null;
 					}
diff --git a/chrome/content/zotero/xpcom/proxy.js b/chrome/content/zotero/xpcom/proxy.js
index ab74dc606f..2de3b54b8d 100644
--- a/chrome/content/zotero/xpcom/proxy.js
+++ b/chrome/content/zotero/xpcom/proxy.js
@@ -50,8 +50,8 @@ Zotero.Proxies = new function() {
 			var me = this;
 			Zotero.MIMETypeHandler.addObserver(function(ch) { me.observe(ch) });
 			
-			var rows = Zotero.DB.query("SELECT * FROM proxies");
-			Zotero.Proxies.proxies = [new Zotero.Proxy(row) for each(row in rows)];
+			var rows = Zotero.DB.query("SELECT * FROM proxies") || [];
+			Zotero.Proxies.proxies = rows.map(row => new Zotero.Proxy(row));
 			
 			for each(var proxy in Zotero.Proxies.proxies) {
 				for each(var host in proxy.hosts) {
diff --git a/chrome/content/zotero/xpcom/quickCopy.js b/chrome/content/zotero/xpcom/quickCopy.js
index 121d0f6294..413e036b03 100644
--- a/chrome/content/zotero/xpcom/quickCopy.js
+++ b/chrome/content/zotero/xpcom/quickCopy.js
@@ -367,8 +367,11 @@ Zotero.QuickCopy = new function() {
 			// Copy citations if shift key pressed
 			if (modified) {
 				var csl = Zotero.Styles.get(format.id).getCiteProc(locale);
-				csl.updateItems([item.id for each(item in items)]);
-				var citation = {citationItems:[{id:item.id} for each(item in items)], properties:{}};
+				csl.updateItems(items.map(item => item.id));
+				var citation = {
+					citationItems: items.map(item => item.id),
+					properties: {}
+				};
 				var html = csl.previewCitationCluster(citation, [], [], "html"); 
 				var text = csl.previewCitationCluster(citation, [], [], "text"); 
 			} else {
diff --git a/chrome/content/zotero/xpcom/server_connector.js b/chrome/content/zotero/xpcom/server_connector.js
index 703a7dceed..ecdf6db33c 100644
--- a/chrome/content/zotero/xpcom/server_connector.js
+++ b/chrome/content/zotero/xpcom/server_connector.js
@@ -509,7 +509,7 @@ Zotero.Server.Connector.Progress.prototype = {
 	 */
 	"init":function(data, sendResponseCallback) {
 		sendResponseCallback(200, "application/json",
-			JSON.stringify([Zotero.Server.Connector.AttachmentProgressManager.getProgressForID(id) for each(id in data)]));
+			JSON.stringify(data.map(id => Zotero.Server.Connector.AttachmentProgressManager.getProgressForID(id))));
 	}
 };
 
diff --git a/chrome/content/zotero/xpcom/storage.js b/chrome/content/zotero/xpcom/storage.js
index ab0a86238f..395061463d 100644
--- a/chrome/content/zotero/xpcom/storage.js
+++ b/chrome/content/zotero/xpcom/storage.js
@@ -1840,8 +1840,9 @@ Zotero.Sync.Storage = new function () {
 		var itemIDs = Zotero.DB.columnQuery(sql, params) || [];
 		
 		// Get files by open time
-		_uploadCheckFiles.filter(function (x) x.timestamp >= minTime);
-		itemIDs = itemIDs.concat([x.itemID for each(x in _uploadCheckFiles)])
+		itemIDs = itemIDs.concat(
+			_uploadCheckFiles.filter(item => item.timestamp >= minTime).map(item => item.id)
+		);
 		
 		return Zotero.Utilities.arrayUnique(itemIDs);
 	}
diff --git a/chrome/content/zotero/xpcom/storage/request.js b/chrome/content/zotero/xpcom/storage/request.js
index daf8ea7d9a..87b9df4700 100644
--- a/chrome/content/zotero/xpcom/storage/request.js
+++ b/chrome/content/zotero/xpcom/storage/request.js
@@ -199,7 +199,7 @@ Zotero.Sync.Storage.Request.prototype.start = function () {
 	//
 	// The main sync logic is triggered here.
 	
-	Q.all([f(this) for each(f in this._onStart)])
+	Q.all(this._onStart.map(f => f(this)))
 	.then(function (results) {
 		return {
 			localChanges: results.some(function (val) val && val.localChanges == true),
diff --git a/chrome/content/zotero/xpcom/style.js b/chrome/content/zotero/xpcom/style.js
index 6c95ba63b8..3a76b99d6f 100644
--- a/chrome/content/zotero/xpcom/style.js
+++ b/chrome/content/zotero/xpcom/style.js
@@ -581,10 +581,10 @@ Zotero.Style = function(arg) {
 		
 		//In CSL 0.8.1, the "term" attribute on cs:category stored both
 		//citation formats and fields.
-		this.categories = [category.getAttribute("term")
-		for each(category in Zotero.Utilities.xpath(doc,
-			'/csl:style/csl:info[1]/csl:category', Zotero.Styles.ns))
-			if(category.hasAttribute("term"))];
+		this.categories = Zotero.Utilities.xpath(
+			doc, '/csl:style/csl:info[1]/csl:category', Zotero.Styles.ns)
+		.filter(category => category.hasAttribute("term"))
+		.map(category => category.getAttribute("term"));
 	} else {
 		//CSL 1.0 introduced a dedicated "citation-format" attribute on cs:category 
 		this.categories = Zotero.Utilities.xpathText(doc,
diff --git a/chrome/content/zotero/xpcom/sync.js b/chrome/content/zotero/xpcom/sync.js
index 5cfc1a3389..a3de74c703 100644
--- a/chrome/content/zotero/xpcom/sync.js
+++ b/chrome/content/zotero/xpcom/sync.js
@@ -753,7 +753,7 @@ Zotero.Sync.Runner = new function () {
 			errors = [];
 		}
 		
-		errors = [this.parseSyncError(e) for each(e in errors)];
+		errors = errors.map(e => this.parseSyncError(e));
 		_errorsByLibrary = {};
 		
 		var primaryError = this.getPrimaryError(errors);
@@ -787,7 +787,7 @@ Zotero.Sync.Runner = new function () {
 	
 	
 	this.getPrimaryError = function (errors) {
-		errors = [this.parseSyncError(e) for each(e in errors)];
+		errors = errors.map(e => this.parseSyncError(e));
 		
 		// Set highest priority error as the primary (sync error icon)
 		var errorModes = {
diff --git a/chrome/content/zotero/xpcom/translation/translator.js b/chrome/content/zotero/xpcom/translation/translator.js
index e63334f1dc..0dbc864e1a 100644
--- a/chrome/content/zotero/xpcom/translation/translator.js
+++ b/chrome/content/zotero/xpcom/translation/translator.js
@@ -188,7 +188,7 @@ Zotero.Translators = new function() {
 	 */
 	this.getAll = function() {
 		if(!_initialized) this.init();
-		return [translator for each(translator in _translators)];
+		return Object.keys(_translators).map(i => _translators[i]);
 	}
 	
 	/**
diff --git a/chrome/content/zotero/xpcom/utilities_internal.js b/chrome/content/zotero/xpcom/utilities_internal.js
index fcbdfdc873..e3fb16c178 100644
--- a/chrome/content/zotero/xpcom/utilities_internal.js
+++ b/chrome/content/zotero/xpcom/utilities_internal.js
@@ -96,7 +96,11 @@ Zotero.Utilities.Internal = {
 		}
 		
 		// convert the binary hash data to a hex string.
-		return [toHexString(hash.charCodeAt(i)) for (i in hash)].join("");
+		var hexStr;
+		for (let i = 0; i < hash.length; i++) {
+			hexStr += toHexString(hash.charCodeAt(i));
+		}
+		return hexStr;
 	},
 	
 	
@@ -138,10 +142,11 @@ Zotero.Utilities.Internal = {
 						}
 						// Hex string
 						else {
-							deferred.resolve(
-								[toHexString(hash.charCodeAt(i))
-									for (i in hash)].join("")
-							);
+							let hexStr;
+							for (let i = 0; i < hash.length; i++) {
+								hexStr += toHexString(hash.charCodeAt(i));
+							}
+							deferred.resolve(hexStr);
 						}
 					}
 				},
diff --git a/chrome/content/zotero/xpcom/zotero.js b/chrome/content/zotero/xpcom/zotero.js
index 090e42638e..191729ae26 100644
--- a/chrome/content/zotero/xpcom/zotero.js
+++ b/chrome/content/zotero/xpcom/zotero.js
@@ -434,7 +434,8 @@ Components.utils.import("resource://gre/modules/Services.jsm");
 		try {
 			var messages = {};
 			cs.getMessageArray(messages, {});
-			_startupErrors = [msg for each(msg in messages.value) if(_shouldKeepError(msg))];
+			_startupErrors = Object.keys(messages.value).map(i => messages[i])
+				.filter(msg => _shouldKeepError(msg));
 		} catch(e) {
 			Zotero.logError(e);
 		}