diff --git a/chrome/content/zotero/xpcom/sync.js b/chrome/content/zotero/xpcom/sync.js
index b9cdabafe..3586717c4 100644
--- a/chrome/content/zotero/xpcom/sync.js
+++ b/chrome/content/zotero/xpcom/sync.js
@@ -1350,12 +1350,12 @@ Zotero.Sync.Server = new function () {
 				_error(response.firstChild.firstChild.nodeValue);
 			}
 			
-			var xml = xmlhttp.responseText.replace(/^\s*<\?xml.*\?>\s*/, '').trim();
-			
-			// Strip XML declaration and convert to E4X
-			xml = new XML(xml);
-			
 			try {
+				var xml = xmlhttp.responseText.replace(/^\s*<\?xml.*\?>\s*/, '').trim();
+				
+				// Strip XML declaration and convert to E4X
+				xml = new XML(xml);
+				
 				var updateKey = xml.@updateKey.toString();
 				
 				// If no earliest date is provided by the server, the server
@@ -2219,6 +2219,10 @@ Zotero.Sync.Server = new function () {
 			}
 		}
 		
+		if (e.message == 'script stack space quota is exhausted') {
+			var e = "Firefox 4.0 or higher is required to process sync operations of this size.";
+		}
+		
 		if (extraInfo) {
 			// Server errors will generally be HTML
 			extraInfo = Zotero.Utilities.unescapeHTML(extraInfo);