diff --git a/src/gui/MainWindow.cpp b/src/gui/MainWindow.cpp
index ea759805e..d050529f8 100644
--- a/src/gui/MainWindow.cpp
+++ b/src/gui/MainWindow.cpp
@@ -72,7 +72,7 @@ MainWindow::MainWindow()
 
     m_inactivityTimer = new InactivityTimer(this);
     connect(m_inactivityTimer, SIGNAL(inactivityDetected()),
-            m_ui->tabWidget, SLOT(lockDatabases()));
+            this, SLOT(lockDatabasesAfterInactivity()));
     applySettingsChanges();
 
     setShortcut(m_ui->actionDatabaseOpen, QKeySequence::Open, Qt::CTRL + Qt::Key_O);
@@ -579,6 +579,16 @@ void MainWindow::toggleWindow()
     }
 }
 
+void MainWindow::lockDatabasesAfterInactivity()
+{
+    // ignore event if a modal dialog is open (such as a message box or file dialog)
+    if (QApplication::activeModalWidget()) {
+        return;
+    }
+
+    m_ui->tabWidget->lockDatabases();
+}
+
 bool MainWindow::isTrayIconEnabled() const
 {
     return config()->get("GUI/ShowTrayIcon").toBool()
diff --git a/src/gui/MainWindow.h b/src/gui/MainWindow.h
index b966703d1..695c20d41 100644
--- a/src/gui/MainWindow.h
+++ b/src/gui/MainWindow.h
@@ -65,6 +65,7 @@ private Q_SLOTS:
     void applySettingsChanges();
     void trayIconTriggered(QSystemTrayIcon::ActivationReason reason);
     void toggleWindow();
+    void lockDatabasesAfterInactivity();
 
 private:
     static void setShortcut(QAction* action, QKeySequence::StandardKey standard, int fallback = 0);