diff --git a/src/internal/sio_client_impl.cpp b/src/internal/sio_client_impl.cpp
index 11f8914f..2eab3ad5 100644
--- a/src/internal/sio_client_impl.cpp
+++ b/src/internal/sio_client_impl.cpp
@@ -222,7 +222,7 @@ namespace sio
             } else {
                 ss<<uo.get_host();
             }
-            ss<<":"<<uo.get_port()<<"/socket.io/?EIO=4&transport=websocket";
+            ss<<":"<<uo.get_port()<<"/socket.io/?EIO=3&transport=websocket";
             if(m_sid.size()>0){
                 ss<<"&sid="<<m_sid;
             }