diff --git a/src/lib/client/Client.cpp b/src/lib/client/Client.cpp
index 673e2bd68..272e64125 100644
--- a/src/lib/client/Client.cpp
+++ b/src/lib/client/Client.cpp
@@ -15,6 +15,7 @@
 #include "common/NetworkProtocol.h"
 #include "common/Settings.h"
 #include "deskflow/Clipboard.h"
+#include "deskflow/DeskflowException.h"
 #include "deskflow/IPlatformScreen.h"
 #include "deskflow/PacketStreamFilter.h"
 #include "deskflow/ProtocolTypes.h"
@@ -632,14 +633,29 @@ void Client::handleHello()
     return;
   }
 
-  LOG_DEBUG(
-      "saying hello back with version %s %d.%d", protocolName.c_str(), kProtocolMajorVersion, kProtocolMinorVersion
-  );
+  if (serverMajor != kProtocolMajorVersion) {
+    LOG_WARN("server protocol version not compatible: %d.%d", serverMajor, serverMinor);
+    sendConnectionFailedEvent(IncompatibleClientException(serverMajor, serverMinor).what());
+    cleanupTimer();
+    cleanupConnection();
+    return;
+  }
+
+  int16_t helloBackMinor = kProtocolMinorVersion;
+  if (serverMinor < kProtocolMinorVersion) {
+    helloBackMinor = serverMinor;
+    LOG_INFO(
+        "downgrading client protocol version from %d.%d to %d.%d", //
+        kProtocolMajorVersion, kProtocolMinorVersion, kProtocolMajorVersion, helloBackMinor
+    );
+  }
+
+  LOG_DEBUG("saying hello back with version %s %d.%d", protocolName.c_str(), kProtocolMajorVersion, helloBackMinor);
 
   // dynamically build write format for hello back since `ProtocolUtil::writef`
   // doesn't support formatting fixed length strings yet.
   std::string helloBackMessage = protocolName + kMsgHelloBackArgs;
-  ProtocolUtil::writef(m_stream, helloBackMessage.c_str(), kProtocolMajorVersion, kProtocolMinorVersion, &m_name);
+  ProtocolUtil::writef(m_stream, helloBackMessage.c_str(), kProtocolMajorVersion, helloBackMinor, &m_name);
 
   // now connected but waiting to complete handshake
   setupScreen();