diff --git a/chrome/content/zotero/xpcom/sync.js b/chrome/content/zotero/xpcom/sync.js
index 1c7af5747a..b97d3c3c3c 100644
--- a/chrome/content/zotero/xpcom/sync.js
+++ b/chrome/content/zotero/xpcom/sync.js
@@ -785,9 +785,15 @@ Zotero.Sync.Runner = new function () {
 		if (status == 'warning' || status == 'error') {
 			icon.setAttribute('status', '');
 			warning.hidden = false;
-			warning.setAttribute('mode', status);
-			warning.setAttribute('error', status == 'error');
-			warning.tooltipText = "A sync error occurred. Click to view details.";
+			if (Zotero.Sync.Server.upgradeRequired) {
+				Zotero.Sync.Server.upgradeRequired = false;
+				warning.setAttribute('mode', 'upgrade');
+				buttonText = null;
+			}
+			else {
+				warning.setAttribute('mode', status);
+			}
+			warning.tooltipText = message;
 			warning.onclick = function () {
 				var wm = Components.classes["@mozilla.org/appshell/window-mediator;1"]
 							.getService(Components.interfaces.nsIWindowMediator);
@@ -1132,6 +1138,7 @@ Zotero.Sync.Server = new function () {
 	
 	this.canAutoResetClient = true;
 	this.manualSyncRequired = false;
+	this.upgradeRequired = false;
 	this.nextLocalSyncDate = false;
 	this.apiVersion = 8;
 	
@@ -1823,6 +1830,10 @@ Zotero.Sync.Server = new function () {
 						}
 					}
 					break;
+				
+				case 'UPGRADE_REQUIRED':
+					Zotero.Sync.Server.upgradeRequired = true;
+					break;
 			}
 		}
 	}
diff --git a/chrome/skin/default/zotero/bell_error.png b/chrome/skin/default/zotero/bell_error.png
new file mode 100644
index 0000000000..a0ddc00281
Binary files /dev/null and b/chrome/skin/default/zotero/bell_error.png differ
diff --git a/chrome/skin/default/zotero/overlay.css b/chrome/skin/default/zotero/overlay.css
index 95122257d0..b88ed1d982 100644
--- a/chrome/skin/default/zotero/overlay.css
+++ b/chrome/skin/default/zotero/overlay.css
@@ -212,17 +212,22 @@
 	font-weight: bold;
 }
 
-#zotero-tb-sync-warning
+#zotero-tb-sync-warning, #zotero-tb-sync-warning[mode=warning]
 {
 	list-style-image: url(chrome://zotero/skin/error.png);
 	margin-right: -5px;
 }
 
-#zotero-tb-sync-warning[error=true]
+#zotero-tb-sync-warning[mode=error]
 {
 	list-style-image: url(chrome://zotero/skin/exclamation.png);
 }
 
+#zotero-tb-sync-warning[mode=upgrade]
+{
+	list-style-image: url(chrome://zotero/skin/bell_error.png);
+}
+
 #zotero-tb-sync {
 	list-style-image: url(chrome://zotero/skin/arrow_rotate_static.png);
 	margin-left: -2px;