diff --git a/src/net/login/GruntLogin.cpp b/src/net/login/GruntLogin.cpp
index df12947..2811a12 100644
--- a/src/net/login/GruntLogin.cpp
+++ b/src/net/login/GruntLogin.cpp
@@ -49,6 +49,12 @@ void GruntLogin::GetLogonMethod() {
     logon.version[2] = 5;
     logon.build = 12340;
 
+#if defined(WHOA_SYSTEM_WIN)
+    logon.osID = '\0Win';
+#elif defined(WHOA_SYSTEM_MAC)
+    logon.osID = '\0OSX';
+#endif
+
     // TODO
 
     if (this->IsReconnect()) {