diff --git a/pc/code_twain/sln/usb_tools/Debug/usb_tools.exe b/pc/code_twain/sln/usb_tools/Debug/usb_tools.exe
index c38b6d8..4bf4a45 100644
Binary files a/pc/code_twain/sln/usb_tools/Debug/usb_tools.exe and b/pc/code_twain/sln/usb_tools/Debug/usb_tools.exe differ
diff --git a/pc/code_twain/sln/usb_tools/DlgScanner.cpp b/pc/code_twain/sln/usb_tools/DlgScanner.cpp
index 9a320d1..3dbfab9 100644
--- a/pc/code_twain/sln/usb_tools/DlgScanner.cpp
+++ b/pc/code_twain/sln/usb_tools/DlgScanner.cpp
@@ -667,9 +667,6 @@ void CDlgScanner::set_device(usb::LPUSBPNP pnp)
 	KillTimer(TIMER_ID_REFRESH_BULK);
 	((CButton*)GetDlgItem(IDC_CHECK_AUTO))->SetCheck(BST_UNCHECKED);
 	enable_buttons(pnp != NULL);
-	GetDlgItem(IDC_CHECK_AUTO)->EnableWindow(pnp != NULL);
-	GetDlgItem(IDC_BUTTON_RESET_BULK)->EnableWindow(pnp != NULL);
-	GetDlgItem(IDC_BUTTON_REFRESH)->EnableWindow(pnp != NULL);
 
 	if (scanner_)
 	{
@@ -767,15 +764,18 @@ void CDlgScanner::set_device(usb::LPUSBPNP pnp)
 		else
 		{
 			wchar_t	buf[128] = { 0 };
-			uint8_t	h = 0, l = 0;
+			uint16_t	ver = 0;
 
 			swprintf_s(buf, _countof(buf) - 1, L"%04X:%04X", pnp->vid, pnp->pid);
 			::SetWindowTextW(m_hWnd, buf);
 
-			err = scanner_->get_protocol_version(&h, &l);
-			if (err)
+			err = scanner_->get_protocol_version(&ver);
+			if (err || ver != PROTOCOL_VER)
 			{
-				msg_box(m_hWnd, MB_OK, L"Unsupported Scanner", L"Failed to get protocol version with error %d.", err);
+				if(err)
+					msg_box(m_hWnd, MB_OK, L"Unsupported Scanner", L"Failed to get protocol version with error %d.", err);
+				else
+					msg_box(m_hWnd, MB_OK, L"Unsupported Scanner", L"Protocol version is mismatch: expect %u.%u but return %u.%u", HIBYTE(PROTOCOL_VER), LOBYTE(PROTOCOL_VER), HIBYTE(ver), LOBYTE(ver));
 				scanner_->release();
 				scanner_ = NULL;
 				enable_buttons(false);
@@ -784,7 +784,7 @@ void CDlgScanner::set_device(usb::LPUSBPNP pnp)
 			{
 				scanner_->set_image_receiver(img_keeper);
 
-				swprintf_s(buf, _countof(buf) - 1, L"%u.%u", h, l);
+				swprintf_s(buf, _countof(buf) - 1, L"%u.%u", HIBYTE(ver), LOBYTE(ver));
 				SetDlgItemTextW(IDC_EDIT_PROTOCOL_VER, buf);
 
 				refresh_bulk_status();
@@ -815,6 +815,9 @@ void CDlgScanner::set_device(usb::LPUSBPNP pnp)
 	{
 		::SetDlgItemTextW(m_hWnd, IDC_BUTTON_SCAN, L"Scan");
 	}
+	GetDlgItem(IDC_CHECK_AUTO)->EnableWindow(scanner_ != NULL);
+	GetDlgItem(IDC_BUTTON_RESET_BULK)->EnableWindow(scanner_ != NULL);
+	GetDlgItem(IDC_BUTTON_REFRESH)->EnableWindow(scanner_ != NULL);
 }
 void CDlgScanner::get_option(const char* name, void* value, size_t size)
 {
diff --git a/pc/code_twain/sln/usb_tools/scanner/scanner_handler.cpp b/pc/code_twain/sln/usb_tools/scanner/scanner_handler.cpp
index 2376be6..b9d0789 100644
--- a/pc/code_twain/sln/usb_tools/scanner/scanner_handler.cpp
+++ b/pc/code_twain/sln/usb_tools/scanner/scanner_handler.cpp
@@ -415,12 +415,12 @@ int scanner_handler::wait_result(cmd_result* reply)
 	}
 }
 
-int scanner_handler::get_protocol_version(uint8_t* h, uint8_t* l)
+int scanner_handler::get_protocol_version(uint16_t* ver)
 {
 	if (!is_scanner_available())
 		return ENODEV;
 
-	return usb_->get_peer_protocol_version(h, l);
+	return usb_->get_peer_protocol_version(ver);
 }
 int scanner_handler::get_scanner_status(LPEP0REPLYSTATUS status)
 {
diff --git a/pc/code_twain/sln/usb_tools/scanner/scanner_handler.h b/pc/code_twain/sln/usb_tools/scanner/scanner_handler.h
index 943cbe2..118fb2f 100644
--- a/pc/code_twain/sln/usb_tools/scanner/scanner_handler.h
+++ b/pc/code_twain/sln/usb_tools/scanner/scanner_handler.h
@@ -101,7 +101,7 @@ protected:
 	// I/O ...
 public:
 	// following methods transferred by EP0
-	int get_protocol_version(uint8_t* h, uint8_t* l);
+	int get_protocol_version(uint16_t* ver);
 	int get_scanner_status(LPEP0REPLYSTATUS status);
 	int restart_peer_bulk(uint32_t timeout = 1000/*ms*/);
 
diff --git a/pc/code_twain/sln/usb_tools/scanner/usb/async_usb_host.cpp b/pc/code_twain/sln/usb_tools/scanner/usb/async_usb_host.cpp
index dee692f..dbe0d4e 100644
--- a/pc/code_twain/sln/usb_tools/scanner/usb/async_usb_host.cpp
+++ b/pc/code_twain/sln/usb_tools/scanner/usb/async_usb_host.cpp
@@ -479,20 +479,18 @@ dyn_mem_ptr async_usb_host::handle_data_in(dyn_mem_ptr& data, uint32_t* used, pa
 	}
 }
 
-int async_usb_host::get_peer_protocol_version(uint8_t* main, uint8_t* sub)
+int async_usb_host::get_peer_protocol_version(uint16_t* ver)
 {
-	uint16_t	ver = 0;
+	uint16_t	v = 0;
 	int			err = libusb_control_transfer(usb_handle_, LIBUSB_REQUEST_TYPE_VENDOR | LIBUSB_ENDPOINT_IN
 											, USB_REQ_EP0_GET_PROTO_VER, 0, 0
-											, (unsigned char*)&ver, sizeof(ver)
+											, (unsigned char*)&v, sizeof(v)
 											, 1000);
 
-	if (main)
-		*main = (ver >> 8) & 0x0ff;
-	if (sub)
-		*sub = ver & 0x0ff;
+	if (ver)
+		*ver = v;
 
-	return err == sizeof(ver) ? 0 : EFAULT;
+	return err == sizeof(v) ? 0 : EFAULT;
 }
 int async_usb_host::get_peer_status(LPEP0REPLYSTATUS status)
 {
diff --git a/pc/code_twain/sln/usb_tools/scanner/usb/async_usb_host.h b/pc/code_twain/sln/usb_tools/scanner/usb/async_usb_host.h
index 67bcff6..2129f38 100644
--- a/pc/code_twain/sln/usb_tools/scanner/usb/async_usb_host.h
+++ b/pc/code_twain/sln/usb_tools/scanner/usb/async_usb_host.h
@@ -77,7 +77,7 @@ public:
 	uint8_t& encrypt_data(void);
 
 public:
-	int get_peer_protocol_version(uint8_t* main, uint8_t* sub);
+	int get_peer_protocol_version(uint16_t* ver);
 	int get_peer_status(LPEP0REPLYSTATUS status);
 	int restart_peer_bulk(uint32_t timeout = 1000/*ms*/);
 	int set_gadget_encrypting_method(uint32_t cmd_enc = ENCRYPT_CMD_NONE, uint32_t payload_enc = ENCRYPT_NONE, uint8_t enc_data = 0);