diff --git a/navalplanner-webapp/src/main/java/org/navalplanner/web/calendars/BaseCalendarModel.java b/navalplanner-webapp/src/main/java/org/navalplanner/web/calendars/BaseCalendarModel.java
index 54cffdb15..3bafa8d15 100644
--- a/navalplanner-webapp/src/main/java/org/navalplanner/web/calendars/BaseCalendarModel.java
+++ b/navalplanner-webapp/src/main/java/org/navalplanner/web/calendars/BaseCalendarModel.java
@@ -566,6 +566,9 @@ public class BaseCalendarModel extends IntegrationEntityModel implements
 
     @Override
     public boolean isOwnException(CalendarException exception) {
+        if (getBaseCalendar() == null) {
+            return false;
+        }
         return getBaseCalendar().getOwnExceptions().contains(exception);
     }