diff --git a/modules/twainui/dialog_progress_ui.cpp b/modules/twainui/dialog_progress_ui.cpp
index 8a3403c3..8b4d55ba 100644
--- a/modules/twainui/dialog_progress_ui.cpp
+++ b/modules/twainui/dialog_progress_ui.cpp
@@ -77,6 +77,9 @@ void Dialog_progress_ui::closeEvent(QCloseEvent* e)
 
 void Dialog_progress_ui::on_pbtn_cancelScan_clicked()
 {
+    if (!m_isScanning)
+        return;
+
     if (!quit_)
     {
         HGBase_OpenThread(CancelScanThreadFunc, this, &m_thread_cancelScan);