diff --git a/src/org/p2pvpn/gui/CalendarPopup.java b/src/org/p2pvpn/gui/CalendarPopup.java
index c62028d..7d6aaab 100644
--- a/src/org/p2pvpn/gui/CalendarPopup.java
+++ b/src/org/p2pvpn/gui/CalendarPopup.java
@@ -30,6 +30,7 @@ import java.time.LocalDate;
 import java.time.LocalDateTime;
 import java.time.ZoneId;
 import java.util.Date;
+import javax.swing.BorderFactory;
 import javax.swing.JSpinner;
 import javax.swing.SwingUtilities;
 import javax.swing.UIManager;
@@ -65,7 +66,7 @@ public class CalendarPopup implements CalendarListener {
                 calendarPanel,
                 SwingUtilities.getWindowAncestor(parentComponent),
                 null,
-                null);
+                BorderFactory.createLineBorder(UIManager.getColor("Table.selectionBackground")));
 
         Point pointOnScreen = new Point(); 
         SwingUtilities.convertPointToScreen(pointOnScreen, parentComponent);