diff --git a/CMakeLists.txt b/CMakeLists.txt
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -41,7 +41,7 @@
 
 set(AKONADI_MIMELIB_VERSION "5.11.40")
 set(AKONADI_CONTACT_VERSION "5.11.40")
-set(KCALENDARCORE_LIB_VERSION "5.11.42")
+set(KCALENDARCORE_LIB_VERSION "5.11.44")
 set(IDENTITYMANAGEMENT_LIB_VERSION "5.11.40")
 set(KLDAP_LIB_VERSION "5.11.40")
 set(KMAILTRANSPORT_LIB_VERSION "5.11.40")
diff --git a/korgac/mailclient.cpp b/korgac/mailclient.cpp
--- a/korgac/mailclient.cpp
+++ b/korgac/mailclient.cpp
@@ -61,7 +61,7 @@
 
 bool MailClient::mailAttendees(const KCalCore::IncidenceBase::Ptr &incidence, const KIdentityManagement::Identity &identity, bool bccMe, const QString &attachment, const QString &mailTransport)
 {
-    KCalCore::Attendee::List attendees = incidence->attendees();
+    const KCalCore::Attendee::List attendees = incidence->attendees();
     if (attendees.isEmpty()) {
         qCWarning(KOALARMCLIENT_LOG) << "There are no attendees to e-mail";
         return false;
@@ -72,11 +72,8 @@
 
     QStringList toList;
     QStringList ccList;
-    const int numberOfAttendees(attendees.count());
-    for (int i = 0; i < numberOfAttendees; ++i) {
-        KCalCore::Attendee::Ptr a = attendees.at(i);
-
-        const QString email = a->email();
+    for (const auto &a : attendees) {
+        const QString email = a.email();
         if (email.isEmpty()) {
             continue;
         }
@@ -90,15 +87,15 @@
 
         // Build a nice address for this attendee including the CN.
         QString tname, temail;
-        const QString username = KEmailAddress::quoteNameIfNecessary(a->name());
+        const QString username = KEmailAddress::quoteNameIfNecessary(a.name());
         // ignore the return value from extractEmailAddressAndName() because
         // it will always be false since tusername does not contain "@domain".
         KEmailAddress::extractEmailAddressAndName(username, temail /*byref*/, tname /*byref*/);
         tname += QStringLiteral(" <") + email + QLatin1Char('>');
 
         // Optional Participants and Non-Participants are copied on the email
-        if (a->role() == KCalCore::Attendee::OptParticipant
-            || a->role() == KCalCore::Attendee::NonParticipant) {
+        if (a.role() == KCalCore::Attendee::OptParticipant
+            || a.role() == KCalCore::Attendee::NonParticipant) {
             ccList << tname;
         } else {
             toList << tname;
diff --git a/src/calendarview.cpp b/src/calendarview.cpp
--- a/src/calendarview.cpp
+++ b/src/calendarview.cpp
@@ -1896,8 +1896,8 @@
 
     const bool organizerEvents
         = CalendarSupport::KCalPrefs::instance()->thatIsMe(incidence->organizer().email());
-    const bool groupEvents = incidence->attendeeByMails(
-        CalendarSupport::KCalPrefs::instance()->allEmails());
+    const bool groupEvents = !incidence->attendeeByMails(
+        CalendarSupport::KCalPrefs::instance()->allEmails()).isNull();
 
     if (incidence->type() == KCalCore::Incidence::TypeTodo) {
         todo = true;
diff --git a/src/dialog/searchdialog.cpp b/src/dialog/searchdialog.cpp
--- a/src/dialog/searchdialog.cpp
+++ b/src/dialog/searchdialog.cpp
@@ -243,8 +243,8 @@
         }
         if (m_ui->attendeeCheck->isChecked()) {
             const KCalCore::Attendee::List lstAttendees = ev->attendees();
-            for (const KCalCore::Attendee::Ptr &attendee : lstAttendees) {
-                if (re.indexIn(attendee->fullName()) != -1) {
+            for (const KCalCore::Attendee &attendee : lstAttendees) {
+                if (re.indexIn(attendee.fullName()) != -1) {
                     mMatchedEvents.append(item);
                     break;
                 }