diff --git a/chrome/content/zotero/xpcom/zotero.js b/chrome/content/zotero/xpcom/zotero.js
index e94b4241fb..a2f53f07b1 100644
--- a/chrome/content/zotero/xpcom/zotero.js
+++ b/chrome/content/zotero/xpcom/zotero.js
@@ -235,10 +235,11 @@ Services.scriptloader.loadSubScript("resource://zotero/polyfill.js");
 			   .getService(Components.interfaces.nsIAppShellService)
 			   .hiddenDOMWindow;
 		this.platform = win.navigator.platform;
-		this.isMac = (this.platform.substr(0, 3) == "Mac");
+		this.isMac = this.platform.substr(0, 3) == "Mac";
 		this.isWin = (this.platform.substr(0, 3) == "Win");
 		this.isLinux = (this.platform.substr(0, 5) == "Linux");
 		this.oscpu = win.navigator.oscpu;
+		this.isBigSurOrLater = this.isMac && !/Mac OS X 10.([1-9]|1[0-5])/.test(win.navigator.oscpu);
 		
 		// Browser
 		Zotero.browser = "g";