diff --git a/sources/main.cpp b/sources/main.cpp
index eede1bfb8..e723d0d43 100644
--- a/sources/main.cpp
+++ b/sources/main.cpp
@@ -19,6 +19,7 @@
 #include "machine_info.h"
 #include "qet.h"
 #include "qetapp.h"
+#include "qetmessagebox.h"
 #include "qetproject.h"
 #include "singleapplication.h"
 #include "utils/qetsettings.h"
@@ -249,6 +250,11 @@ QGuiApplication::setHighDpiScaleFactorRoundingPolicy(QetSettings::hdpiScaleFacto
 			// runs on a background thread referencing the project and races the
 			// process exit (intermittent segfault in QET::writeToFile).
 			QETProject::setBackupEnabled(false);
+			// Answer message boxes instead of showing them: opening a project
+			// saved by an older QElectroTech raises a warning from
+			// QETProject::readProjectXml(), and with nobody able to dismiss it
+			// QDialog::exec() would spin its event loop forever.
+			QET::QetMessageBox::setNonInteractive(true);
 			return CLIExport::run(export_app.arguments());
 		}
 	}
diff --git a/sources/qetmessagebox.cpp b/sources/qetmessagebox.cpp
index 31d6e41a8..2731baf00 100644
--- a/sources/qetmessagebox.cpp
+++ b/sources/qetmessagebox.cpp
@@ -17,6 +17,84 @@
 */
 #include "qetmessagebox.h"
 
+#include <QTextStream>
+
+namespace {
+	bool g_non_interactive = false;
+
+	/**
+		@brief autoAnswer
+		Report a message box on stderr and pick an answer, for use when there
+		is no user to click anything. @see QET::QetMessageBox::setNonInteractive
+		@param severity : short word naming the kind of box, for the log line
+		@param title
+		@param text
+		@param buttons : the buttons the caller offered
+		@param defaultButton : the caller's preferred answer, may be NoButton
+		@return the button to report as pressed
+	*/
+	QMessageBox::StandardButton autoAnswer(
+			const char *severity,
+			const QString &title,
+			const QString &text,
+			QMessageBox::StandardButtons buttons,
+			QMessageBox::StandardButton defaultButton)
+	{
+			//Honour the caller's own default when it named one.
+		if (defaultButton != QMessageBox::NoButton
+			&& (buttons & defaultButton)) {
+			QTextStream(stderr) << severity << ": " << title << " -- " << text
+								<< "\n(no display: answered with the caller's default button)\n";
+			return defaultButton;
+		}
+
+			//Otherwise prefer a "carry on" answer over one that cancels, so a
+			//batch run completes rather than silently doing nothing.
+		static const QMessageBox::StandardButton preference[] = {
+			QMessageBox::Ok,     QMessageBox::Open,   QMessageBox::Yes,
+			QMessageBox::Save,   QMessageBox::Apply,  QMessageBox::YesToAll,
+			QMessageBox::Retry,  QMessageBox::Ignore, QMessageBox::Close
+		};
+		for (auto candidate : preference) {
+			if (buttons & candidate) {
+				QTextStream(stderr) << severity << ": " << title << " -- " << text
+									<< "\n(no display: continuing)\n";
+				return candidate;
+			}
+		}
+
+			//Nothing affirmative on offer -- fall back to whatever is set.
+		for (int bit = QMessageBox::Ok; bit <= QMessageBox::RestoreDefaults; bit <<= 1) {
+			auto candidate = static_cast<QMessageBox::StandardButton>(bit);
+			if (buttons & candidate) {
+				QTextStream(stderr) << severity << ": " << title << " -- " << text
+									<< "\n(no display: answered automatically)\n";
+				return candidate;
+			}
+		}
+
+		QTextStream(stderr) << severity << ": " << title << " -- " << text
+							<< "\n(no display: no button offered)\n";
+		return QMessageBox::NoButton;
+	}
+}
+
+/**
+	@brief QET::QetMessageBox::setNonInteractive
+	@param non_interactive
+*/
+void QET::QetMessageBox::setNonInteractive(bool non_interactive) {
+	g_non_interactive = non_interactive;
+}
+
+/**
+	@brief QET::QetMessageBox::isNonInteractive
+	@return true when message boxes are answered without a user
+*/
+bool QET::QetMessageBox::isNonInteractive() {
+	return g_non_interactive;
+}
+
 /**
 	@see Documentation Qt pour QMessageBox::critical
 */
@@ -27,6 +105,9 @@ QMessageBox::StandardButton QET::QetMessageBox::critical (
 		QMessageBox::StandardButtons buttons,
 		QMessageBox::StandardButton defaultButton)
 {
+	if (g_non_interactive) {
+		return autoAnswer("Critical", title, text, buttons, defaultButton);
+	}
 #ifdef Q_OS_MACOS
 	QMessageBox message_box(
 				QMessageBox::Critical,
@@ -59,6 +140,9 @@ QMessageBox::StandardButton QET::QetMessageBox::information(
 		QMessageBox::StandardButtons buttons,
 		QMessageBox::StandardButton defaultButton)
 {
+	if (g_non_interactive) {
+		return autoAnswer("Information", title, text, buttons, defaultButton);
+	}
 #ifdef Q_OS_MACOS
 	QMessageBox message_box(
 				QMessageBox::Information,
@@ -91,6 +175,9 @@ QMessageBox::StandardButton QET::QetMessageBox::question (
 		QMessageBox::StandardButtons buttons,
 		QMessageBox::StandardButton defaultButton)
 {
+	if (g_non_interactive) {
+		return autoAnswer("Question", title, text, buttons, defaultButton);
+	}
 #ifdef Q_OS_MACOS
 	QMessageBox message_box(
 				QMessageBox::Question,
@@ -123,6 +210,9 @@ QMessageBox::StandardButton QET::QetMessageBox::warning (
 		QMessageBox::StandardButtons buttons,
 		QMessageBox::StandardButton defaultButton)
 {
+	if (g_non_interactive) {
+		return autoAnswer("Warning", title, text, buttons, defaultButton);
+	}
 #ifdef Q_OS_MACOS
 	QMessageBox message_box(
 				QMessageBox::Warning,
diff --git a/sources/qetmessagebox.h b/sources/qetmessagebox.h
index 60238595a..6e838f4e4 100644
--- a/sources/qetmessagebox.h
+++ b/sources/qetmessagebox.h
@@ -27,6 +27,28 @@ namespace QET {
 		Qt:Sheet flag, thus enabling a better MacOS integration.
 	*/
 	namespace QetMessageBox {
+		/**
+			Enable non-interactive mode.
+
+			In non-interactive mode the functions below never construct a
+			dialog. They write the message to stderr and return an answer
+			immediately, so a headless run cannot block on a modal box that
+			nobody is there to dismiss.
+
+			This is needed because these are reachable from the command-line
+			tools: opening a project written by an older QElectroTech raises
+			a warning from QETProject::readProjectXml(), and with no display
+			to click it, QDialog::exec() spins its event loop forever.
+
+			The answer is chosen as: the caller's defaultButton when it gave
+			one, otherwise the first "carry on" button among those offered
+			(Ok, Open, Yes, Save, Apply...), otherwise the first button set.
+			So the two warnings above resolve to Open and the project loads,
+			which is what a batch invocation wants.
+		*/
+		void setNonInteractive(bool non_interactive);
+		bool isNonInteractive();
+
 		QMessageBox::StandardButton critical (
 				QWidget *,
 				const QString &,