diff --git a/calendaring/event.cpp b/calendaring/event.cpp
--- a/calendaring/event.cpp
+++ b/calendaring/event.cpp
@@ -76,17 +76,22 @@
 void Event::delegate(const std::vector< Attendee >& delegators, const std::vector< Attendee >& delegatees)
 {
 
-    //First build a list of attendee references, and insert any missing attendees
-    std::vector<Kolab::Attendee*> delegateesRef;
+    //First insert any missing attendees
     foreach(const Attendee &a, delegatees) {
-        if (Attendee *attendee = getAttendee(a.contact())) {
-            delegateesRef.push_back(attendee);
-        } else {
+        if (!getAttendee(a.contact())) {
             d->attendees.push_back(a);
-            delegateesRef.push_back(&d->attendees.back());
         }
     }
 
+    //Build a list of attendee references
+    //These are pointers into d->attendees, so we MUST NOT modify that vector after this point!
+    std::vector<Kolab::Attendee*> delegateesRef;
+    foreach(const Attendee &a, delegatees) {
+        Attendee *attendee = getAttendee(a.contact());
+        Q_ASSERT(attendee);
+        delegateesRef.push_back(attendee);
+    }
+
     std::vector<Kolab::Attendee*> delegatorsRef;
     foreach(const Attendee& a, delegators) {
         if (Attendee *attendee = getAttendee(a.contact())) {