diff --git a/src/main/java/com/bybit/api/client/websocket/impl/WebsocketStreamClientImpl.java b/src/main/java/com/bybit/api/client/websocket/impl/WebsocketStreamClientImpl.java
index 644b0a3..53d3531 100644
--- a/src/main/java/com/bybit/api/client/websocket/impl/WebsocketStreamClientImpl.java
+++ b/src/main/java/com/bybit/api/client/websocket/impl/WebsocketStreamClientImpl.java
@@ -264,7 +264,10 @@ private void flushMessageQueue() {
     public void onMessage(String msg) throws JsonProcessingException {
         if (requiresAuthentication(path) && msg.contains("\"op\":\"auth\"")) {
             // Check if authentication was successful
-            isAuthenticated = msg.contains("\"retCode\":0");
+            // Bybit demo trading WS responds with {"success":true,...} (no retCode);
+            // upstream issue #63 — accept either signal as auth success.
+            isAuthenticated = msg.contains("\"retCode\":0")
+                    || (msg.contains("\"success\":true") && msg.contains("\"op\":\"auth\""));
             if (isAuthenticated) {
                 LOGGER.info("Authentication successful.");
                 flushMessageQueue(); // Send queued messages after successful authentication