diff --git a/CMakeLists.txt b/CMakeLists.txt
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -8,7 +8,7 @@
 set(KDEPIMLIBS_VERSION_MAJOR 4)
 set(KDEPIMLIBS_VERSION_MINOR 13)
 set(KDEPIMLIBS_VERSION_PATCH 0)
-set(KDEPIMLIBS_VERSION_KOLAB 24)
+set(KDEPIMLIBS_VERSION_KOLAB 25)
 set(KDEPIMLIBS_VERSION ${KDEPIMLIBS_VERSION_MAJOR}.${KDEPIMLIBS_VERSION_MINOR}.${KDEPIMLIBS_VERSION_PATCH}.${KDEPIMLIBS_VERSION_KOLAB})
 
 
diff --git a/akonadi/calendar/calendarbase.cpp b/akonadi/calendar/calendarbase.cpp
--- a/akonadi/calendar/calendarbase.cpp
+++ b/akonadi/calendar/calendarbase.cpp
@@ -246,8 +246,15 @@
                  << "Please fix it. Ignoring this incidence.";
         return;
     }
-    const QString calendar = QString::number(item.parentCollection().id());
+    QString calendar = QString::number(item.parentCollection().id());
+
+    // With virtual collections, it can happen, that we have exceptions in other calendars that the mainevent.
+    // For displaying all exceptions, we have to save them also in storage collection to have a unified way to get all exceptions.
+    if ((item.parentCollection().id() != item.storageCollectionId()) && (incidence->hasRecurrenceId() || incidence->recurs())) {
+        calendar = QString::number(item.storageCollectionId());
+    }
     Q_ASSERT(!calendar.isEmpty());
+
     const QString uniqueInstanceIdentifier =  calendar + incidence->instanceIdentifier();
 
     if (mItemIdByUniqueInstanceIdentifier.contains(uniqueInstanceIdentifier) && mItemIdByUniqueInstanceIdentifier[uniqueInstanceIdentifier].id() != item.id()) {
@@ -282,21 +289,11 @@
     incidence->setCustomProperty("VOLATILE", "AKONADI-ID", QString::number(item.id()));
     incidence->cancelUpdates();
 
-    // With virtual collections, it can happen, that we have exceptions in other calendars that the mainevent.
-    // For displaying all exceptions, we have to save them also in storage collection to have a unified way to get all exceptions.
-    if ((item.parentCollection().id() != item.storageCollectionId()) && (incidence->hasRecurrenceId() || incidence->recurs())) {
-        const bool result = q->MultiCalendar::addIncidenceToCalendar(QString::number(item.storageCollectionId()), incidence);
-        if (!result) {
-            kError() << "Error adding incidence " << itemToString(item);
-            Q_ASSERT(false);
-        }
-    } else {
-        // Must be the last one due to re-entrancy
-        const bool result = q->MultiCalendar::addIncidenceToCalendar(calendar, incidence);
-        if (!result) {
-            kError() << "Error adding incidence " << itemToString(item);
-            Q_ASSERT(false);
-        }
+    // Must be the last one due to re-entrancy
+    const bool result = q->MultiCalendar::addIncidenceToCalendar(calendar, incidence);
+    if (!result) {
+        kError() << "Error adding incidence " << itemToString(item);
+        Q_ASSERT(false);
     }
 }
 
diff --git a/akonadi/calendar/etmcalendar_p.h b/akonadi/calendar/etmcalendar_p.h
--- a/akonadi/calendar/etmcalendar_p.h
+++ b/akonadi/calendar/etmcalendar_p.h
@@ -173,7 +173,7 @@
 
     QHash<Akonadi::Collection::Id, Akonadi::Collection> mCollections;
     QSet<Akonadi::Collection::Id> mCollectionJobs;
-    QHash<Akonadi::Collection::Id, Akonadi::Item> mItemByStorageCollection;
+    QMultiHash<Akonadi::Collection::Id, Akonadi::Item> mItemByStorageCollection;
 };
 
 }