diff --git a/sane/scanner.cpp b/sane/scanner.cpp
index 968a19a..977d893 100644
--- a/sane/scanner.cpp
+++ b/sane/scanner.cpp
@@ -3494,6 +3494,9 @@ COM_API_IMPLEMENT(scanner, bool, ui_show_setting(HWND parent, bool with_scan, bo
 	events_.clear();
 	ui_notify = std::function<void(int, void*, int)>();
 
+	if (!IsWindowVisible(parent))
+		parent = NULL;
+
 	if (callback::show_setting_ui)
 	{
 		if (with_scan)
@@ -3589,6 +3592,9 @@ COM_API_IMPLEMENT(scanner, bool, ui_show_progress(HWND parent, bool bIndicator))
 	is_bIndicator = bIndicator;
 	if (is_bIndicator)
 		ui_notify = std::function<void(int, void*, int)>();
+	if (!IsWindowVisible(parent))
+		parent = NULL;
+
 	auto ui_process = [this](ui_result res)
 	{
 		int uev = SANE_EVENT_SCAN_FINISHED;