diff --git a/speedtest_worker.js b/speedtest_worker.js
index ad1e94d..814a2ad 100644
--- a/speedtest_worker.js
+++ b/speedtest_worker.js
@@ -130,7 +130,7 @@ this.addEventListener("message", function(e) {
 						// ff more precise with 1 upload stream
 						settings.xhr_ulMultistream = 1;
 					}
-					if (typeof s.xhr_ulMultistream === "undefined") {
+					if (typeof s.ping_allowPerformanceApi === "undefined") {
 						// ff performance API sucks
 						settings.ping_allowPerformanceApi = false;
 					}