diff --git a/js/calExchange.js b/js/calExchange.js
index 58baa2e..8bed36d 100644
--- a/js/calExchange.js
+++ b/js/calExchange.js
@@ -299,7 +299,7 @@ calExchange.prototype = {
 		}
 
 		var xml = req.responseText; // bug 270553
-		xml = xml.replace(/^<\?xml\s+version\s*=\s*(["'])[^\1]+\1[^?]*\?>/, ""); // bug 336551
+		xml = xml.replace(/^<\?xml\s+version\s*=\s*(?:"[^"]+"|'[^']+')[^?]*\?>/, ""); // bug 336551
 		xml = new XML(xml);
 
 		this.sdbg(String(xml) + "\n");