diff --git a/src/core/InactivityTimer.cpp b/src/core/InactivityTimer.cpp
index 762c8720..dd162e69 100644
--- a/src/core/InactivityTimer.cpp
+++ b/src/core/InactivityTimer.cpp
@@ -67,7 +67,14 @@ bool InactivityTimer::eventFilter(QObject* watched, QEvent* event)
 
 void InactivityTimer::timeout()
 {
+    // make sure we don't emit the signal a second time while it's still processed
+    if (!m_emitMutx.tryLock()) {
+        return;
+    }
+
     if (m_active && !m_timer->isActive()) {
         Q_EMIT inactivityDetected();
     }
+
+    m_emitMutx.unlock();
 }
diff --git a/src/core/InactivityTimer.h b/src/core/InactivityTimer.h
index 14e4852b..e0a21e08 100644
--- a/src/core/InactivityTimer.h
+++ b/src/core/InactivityTimer.h
@@ -18,6 +18,7 @@
 #ifndef KEEPASSX_INACTIVITYTIMER_H
 #define KEEPASSX_INACTIVITYTIMER_H
 
+#include <QMutex>
 #include <QObject>
 
 #include "core/Global.h"
@@ -46,6 +47,7 @@ private Q_SLOTS:
 private:
     QTimer* m_timer;
     bool m_active;
+    QMutex m_emitMutx;
 };
 
 #endif // KEEPASSX_INACTIVITYTIMER_H