diff --git a/app/SysTray-X/systrayxicon.cpp b/app/SysTray-X/systrayxicon.cpp
index fd8fe5e..efb778f 100644
--- a/app/SysTray-X/systrayxicon.cpp
+++ b/app/SysTray-X/systrayxicon.cpp
@@ -155,7 +155,11 @@ void    SysTrayXIcon::renderIcon()
         painter.setFont( QFont("Sans") );
 
         QString number = QString::number( m_unread_mail );
+#if QT_VERSION < QT_VERSION_CHECK(5, 13, 0)
         double factor = pixmap.width() / ( 3 * painter.fontMetrics().width( number ) );
+#else
+        double factor = pixmap.width() / ( 3 * painter.fontMetrics().horizontalAdvance( number ) );
+#endif
         QFont font = painter.font();
         font.setPointSizeF( font.pointSizeF() * factor );
         font.setBold( true );