diff --git a/chrome/content/zotero/xpcom/storage.js b/chrome/content/zotero/xpcom/storage.js
index 1c71bbfea..0b663df4c 100644
--- a/chrome/content/zotero/xpcom/storage.js
+++ b/chrome/content/zotero/xpcom/storage.js
@@ -811,8 +811,12 @@ Zotero.Sync.Storage = new function () {
 			var numItems = items.length;
 			var updatedStates = {};
 			
-			// OS.File didn't work reliably before Firefox 23, so use the old code
-			if (Zotero.platformMajorVersion < 23) {
+			// OS.File didn't work reliably before Firefox 23, and on Windows it returns
+			// the access time instead of the modification time until Firefox 25
+			// (https://bugzilla.mozilla.org/show_bug.cgi?id=899436),
+			// so use the old code
+			if (Zotero.platformMajorVersion < 23
+					|| (Zotero.isWin && Zotero.platformMajorVersion < 25)) {
 				Zotero.debug("Performing synchronous file update check");
 				
 				for each(var item in items) {