diff --git a/src/protocollogin.cpp b/src/protocollogin.cpp
index 02903d3..5a632e7 100644
--- a/src/protocollogin.cpp
+++ b/src/protocollogin.cpp
@@ -176,6 +176,14 @@ void ProtocolLogin::onRecvFirstMessage(NetworkMessage& msg)
 		return;
 	}
 
+	uint32_t accountNumberOtClientShallow = msg.get<uint32_t>();
+	if (!accountNumber || accountNumberOtClientShallow != accountNumber) {
+		std::ostringstream ss;
+		ss << "Only clients with protocol " << getClientVersionString(g_game.getClientVersion()) << " allowed!";
+		disconnectClient(ss.str(), version);
+		return;
+	}
+
 	std::string password = msg.getString();
 	if (password.empty()) {
 		disconnectClient("Invalid password.", version);