diff --git a/chrome/content/zotero/lookup.js b/chrome/content/zotero/lookup.js
index a877b3b16..dd97426bb 100644
--- a/chrome/content/zotero/lookup.js
+++ b/chrome/content/zotero/lookup.js
@@ -227,9 +227,11 @@ const Zotero_Lookup = new function () {
 		slPanel.setAttribute("collapsed", !!on);
 
 		// Resize arrow box to fit content
-		var panel = document.getElementById("zotero-lookup-panel");
-		var box = panel.firstChild;
-		panel.sizeTo(box.scrollWidth, box.scrollHeight);
+		if(Zotero.isMac) {
+			var panel = document.getElementById("zotero-lookup-panel");
+			var box = panel.firstChild;
+			panel.sizeTo(box.scrollWidth, box.scrollHeight);
+		}
 
 		dest.focus();
 		return dest;