diff --git a/src/event.h b/src/event.h
--- a/src/event.h
+++ b/src/event.h
@@ -261,8 +261,8 @@
     Event &operator=(const Event &other);
 
     // For polymorfic serialization
-    void serialize(QDataStream &out);
-    void deserialize(QDataStream &in);
+    void serialize(QDataStream &out) const override;
+    void deserialize(QDataStream &in) override;
 
     //@cond PRIVATE
     class Private;
diff --git a/src/event.cpp b/src/event.cpp
--- a/src/event.cpp
+++ b/src/event.cpp
@@ -311,16 +311,8 @@
 
 void Event::virtual_hook(VirtualHook id, void *data)
 {
-    switch (id) {
-    case IncidenceBase::SerializerHook:
-        serialize(*reinterpret_cast<QDataStream *>(data));
-        break;
-    case IncidenceBase::DeserializerHook:
-        deserialize(*reinterpret_cast<QDataStream *>(data));
-        break;
-    default:
-        Q_ASSERT(false);
-    }
+    Q_UNUSED(id);
+    Q_UNUSED(data);
 }
 
 QLatin1String KCalCore::Event::mimeType() const
@@ -338,7 +330,7 @@
     return QLatin1String("view-calendar-day");
 }
 
-void Event::serialize(QDataStream &out)
+void Event::serialize(QDataStream &out) const
 {
     Incidence::serialize(out);
     serializeQDateTimeAsKDateTime(out, d->mDtEnd);
diff --git a/src/incidence.h b/src/incidence.h
--- a/src/incidence.h
+++ b/src/incidence.h
@@ -839,8 +839,8 @@
     */
     IncidenceBase &assign(const IncidenceBase &other) override;
 
-    void serialize(QDataStream &out);
-    void deserialize(QDataStream &in);
+    void serialize(QDataStream &out) const override;
+    void deserialize(QDataStream &in) override;
 
 private:
     /**
diff --git a/src/incidence.cpp b/src/incidence.cpp
--- a/src/incidence.cpp
+++ b/src/incidence.cpp
@@ -1083,7 +1083,7 @@
                          << KCalCore::Journal::journalMimeType();
 }
 
-void Incidence::serialize(QDataStream &out)
+void Incidence::serialize(QDataStream &out) const
 {
     serializeQDateTimeAsKDateTime(out, d->mCreated);
     out << d->mRevision << d->mDescription << d->mDescriptionIsRich << d->mSummary
diff --git a/src/incidencebase.h b/src/incidencebase.h
--- a/src/incidencebase.h
+++ b/src/incidencebase.h
@@ -727,10 +727,16 @@
     */
     virtual IncidenceBase &assign(const IncidenceBase &other);
 
-    enum VirtualHook {
-        SerializerHook,
-        DeserializerHook
-    };
+    /**
+     * Sub-type specific serialization.
+     */
+    virtual void serialize(QDataStream &out) const;
+    /**
+     * Sub-type specific deserialization.
+     */
+    virtual void deserialize(QDataStream &in);
+
+    enum VirtualHook {};
 
     /**
       Standard trick to add virtuals later.
@@ -761,19 +767,13 @@
 
 /**
  * Incidence serializer.
- * Uses the virtual_hook internally to avoid slicing.
- *
- * // TODO_KDE5: Provide a virtual serialize() method, as done with assign() and equals().
  *
  * @since 4.12
  */
 KCALCORE_EXPORT QDataStream &operator<<(QDataStream &out, const KCalCore::IncidenceBase::Ptr &);
 
 /**
  * Incidence deserializer.
- * Uses the virtual_hook internally to avoid slicing.
- *
- * // TODO_KDE5: Provide a virtual serialize() method, as done with assign() and equals().
  *
  * @since 4.12
  */
diff --git a/src/incidencebase.cpp b/src/incidencebase.cpp
--- a/src/incidencebase.cpp
+++ b/src/incidencebase.cpp
@@ -650,6 +650,16 @@
     d->mDirtyFields = dirtyFields;
 }
 
+void IncidenceBase::serialize(QDataStream &out) const
+{
+    Q_UNUSED(out);
+}
+
+void IncidenceBase::deserialize(QDataStream &in)
+{
+    Q_UNUSED(in);
+}
+
 /** static */
 quint32 IncidenceBase::magicSerializationIdentifier()
 {
@@ -677,8 +687,8 @@
         out << attendee;
     }
 
-    // Serialize the sub-class data. In KDE5 we can add new virtuals.
-    i->virtual_hook(KCalCore::IncidenceBase::SerializerHook, &out);
+    // Serialize the sub-class data.
+    i->serialize(out);
 
     return out;
 }
@@ -723,8 +733,8 @@
         i->d->mAttendees.append(attendee);
     }
 
-    // Deserialize the sub-class data. In KDE5 we can add new virtuals.
-    i->virtual_hook(KCalCore::IncidenceBase::DeserializerHook, &in);
+    // Deserialize the sub-class data.
+    i->deserialize(in);
 
     return in;
 }
diff --git a/src/journal.h b/src/journal.h
--- a/src/journal.h
+++ b/src/journal.h
@@ -157,8 +157,8 @@
     Journal &operator=(const Journal &other);
 
     // For polymorfic serialization
-    void serialize(QDataStream &out);
-    void deserialize(QDataStream &in);
+    void serialize(QDataStream &out) const override;
+    void deserialize(QDataStream &in) override;
 
     //@cond PRIVATE
     class Private;
diff --git a/src/journal.cpp b/src/journal.cpp
--- a/src/journal.cpp
+++ b/src/journal.cpp
@@ -103,16 +103,8 @@
 
 void Journal::virtual_hook(VirtualHook id, void *data)
 {
-    switch (id) {
-    case IncidenceBase::SerializerHook:
-        serialize(*reinterpret_cast<QDataStream *>(data));
-        break;
-    case IncidenceBase::DeserializerHook:
-        deserialize(*reinterpret_cast<QDataStream *>(data));
-        break;
-    default:
-        Q_ASSERT(false);
-    }
+    Q_UNUSED(id);
+    Q_UNUSED(data);
 }
 
 QLatin1String Journal::mimeType() const
@@ -131,7 +123,7 @@
     return QLatin1String("view-pim-journal");
 }
 
-void Journal::serialize(QDataStream &out)
+void Journal::serialize(QDataStream &out) const
 {
     Incidence::serialize(out);
 }
diff --git a/src/todo.h b/src/todo.h
--- a/src/todo.h
+++ b/src/todo.h
@@ -347,8 +347,8 @@
     Todo &operator=(const Todo &other);
 
     // For polymorfic serialization
-    void serialize(QDataStream &out);
-    void deserialize(QDataStream &in);
+    void serialize(QDataStream &out) const override;
+    void deserialize(QDataStream &in) override;
 
     //@cond PRIVATE
     class Private;
diff --git a/src/todo.cpp b/src/todo.cpp
--- a/src/todo.cpp
+++ b/src/todo.cpp
@@ -526,16 +526,8 @@
 
 void Todo::virtual_hook(VirtualHook id, void *data)
 {
-    switch (id) {
-    case IncidenceBase::SerializerHook:
-        serialize(*reinterpret_cast<QDataStream *>(data));
-        break;
-    case IncidenceBase::DeserializerHook:
-        deserialize(*reinterpret_cast<QDataStream *>(data));
-        break;
-    default:
-        Q_ASSERT(false);
-    }
+    Q_UNUSED(id);
+    Q_UNUSED(data);
 }
 
 QLatin1String Todo::mimeType() const
@@ -561,7 +553,7 @@
     }
 }
 
-void Todo::serialize(QDataStream &out)
+void Todo::serialize(QDataStream &out) const
 {
     Incidence::serialize(out);
     serializeQDateTimeAsKDateTime(out, d->mDtDue);