diff --git a/CMakeLists.txt b/CMakeLists.txt
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -9,6 +9,7 @@
 include(KDEInstallDirs)
 include(KDECMakeSettings)
 include(KDECompilerSettings)
+include(ECMQtDeclareLoggingCategory)
 
 find_package(Qt5 ${REQUIRED_QT_VERSION} CONFIG REQUIRED Quick Widgets DBus)
 find_package(KF5 ${KF5_MIN_VERSION} REQUIRED COMPONENTS Plasma WindowSystem)
diff --git a/plugin/libdbusmenuqt/CMakeLists.txt b/plugin/libdbusmenuqt/CMakeLists.txt
--- a/plugin/libdbusmenuqt/CMakeLists.txt
+++ b/plugin/libdbusmenuqt/CMakeLists.txt
@@ -5,6 +5,11 @@
 utils.cpp
 )
 
+ecm_qt_declare_logging_category(libdbusmenu_SRCS HEADER debug.h
+                                            IDENTIFIER DBUSMENUQT
+                                            CATEGORY_NAME org.kde.libdbusmenuqt
+                                            DEFAULT_SEVERITY Info)
+
 set_source_files_properties(com.canonical.dbusmenu.xml PROPERTIES
    NO_NAMESPACE true
    INCLUDE "dbusmenutypes_p.h"
@@ -18,3 +23,5 @@
     Qt5::DBus
     Qt5::Widgets
 )
+
+# add_subdirectory(test)
diff --git a/plugin/libdbusmenuqt/com.canonical.dbusmenu.xml b/plugin/libdbusmenuqt/com.canonical.dbusmenu.xml
--- a/plugin/libdbusmenuqt/com.canonical.dbusmenu.xml
+++ b/plugin/libdbusmenuqt/com.canonical.dbusmenu.xml
@@ -2,8 +2,8 @@
     <property name="Version" type="u" access="read"/>
     <property name="Status" type="s" access="read"/>
     <signal name="ItemsPropertiesUpdated">
-    <annotation name="org.qtproject.QtDBus.QtTypeName.In0" value="DBusMenuItemList"/>
-    <annotation name="org.qtproject.QtDBus.QtTypeName.In1" value="DBusMenuItemKeysList"/>
+    <annotation name="org.qtproject.QtDBus.QtTypeName.Out0" value="DBusMenuItemList"/>
+    <annotation name="org.qtproject.QtDBus.QtTypeName.Out1" value="DBusMenuItemKeysList"/>
     <arg type="a(ia{sv})" direction="out"/>
     <arg type="a(ias)" direction="out"/>
     </signal>
diff --git a/plugin/libdbusmenuqt/dbusmenuimporter.h b/plugin/libdbusmenuqt/dbusmenuimporter.h
--- a/plugin/libdbusmenuqt/dbusmenuimporter.h
+++ b/plugin/libdbusmenuqt/dbusmenuimporter.h
@@ -22,7 +22,7 @@
 #define DBUSMENUIMPORTER_H
 
 // Qt
-#include <QtCore/QObject>
+#include <QObject>
 
 class QAction;
 class QDBusPendingCallWatcher;
@@ -43,7 +43,7 @@
     /**
      * Creates a DBusMenuImporter listening over DBus on service, path
      */
-    DBusMenuImporter(const QString &service, const QString &path, QObject *parent = 0);
+    DBusMenuImporter(const QString &service, const QString &path, QObject *parent = nullptr);
 
     ~DBusMenuImporter() override;
 
diff --git a/plugin/libdbusmenuqt/dbusmenuimporter.cpp b/plugin/libdbusmenuqt/dbusmenuimporter.cpp
--- a/plugin/libdbusmenuqt/dbusmenuimporter.cpp
+++ b/plugin/libdbusmenuqt/dbusmenuimporter.cpp
@@ -20,6 +20,8 @@
 */
 #include "dbusmenuimporter.h"
 
+#include "debug.h"
+
 // Qt
 #include <QCoreApplication>
 #include <QDBusConnection>
@@ -46,12 +48,11 @@
 
 //#define BENCHMARK
 #ifdef BENCHMARK
-#include <QTime>
 static QTime sChrono;
 #endif
 
 #define DMRETURN_IF_FAIL(cond) if (!(cond)) { \
-    qWarning() << "Condition failed: " #cond; \
+    qCWarning(DBUSMENUQT) << "Condition failed: " #cond; \
     return; \
 }
 
@@ -61,7 +62,7 @@
 
 static QAction *createKdeTitle(QAction *action, QWidget *parent)
 {
-    QToolButton *titleWidget = new QToolButton(0);
+    QToolButton *titleWidget = new QToolButton(nullptr);
     QFont font = titleWidget->font();
     font.setBold(true);
     titleWidget->setFont(font);
@@ -182,7 +183,7 @@
         } else if (key == QLatin1String("shortcut")) {
             updateActionShortcut(action, value);
         } else {
-            qWarning() << "Unhandled property update" << key;
+            qDebug(DBUSMENUQT) << "Unhandled property update" << key;
         }
     }
 
@@ -230,7 +231,7 @@
         action->setProperty(DBUSMENU_PROPERTY_ICON_DATA_HASH, dataHash);
         QPixmap pix;
         if (!pix.loadFromData(data)) {
-            qWarning() << "Failed to decode icon-data property for action" << action->text();
+            qDebug(DBUSMENUQT) << "Failed to decode icon-data property for action" << action->text();
             action->setIcon(QIcon());
             return;
         }
@@ -258,7 +259,7 @@
         }
         QAction *action = m_actionForId.value(id);
         if (!action) {
-            return 0;
+            return nullptr;
         }
         return action->menu();
     }
@@ -279,7 +280,7 @@
 
     d->q = this;
     d->m_interface = new DBusMenuInterface(service, path, QDBusConnection::sessionBus(), this);
-    d->m_menu = 0;
+    d->m_menu = nullptr;
 
     d->m_pendingLayoutUpdateTimer = new QTimer(this);
     d->m_pendingLayoutUpdateTimer->setSingleShot(true);
@@ -327,7 +328,7 @@
 QMenu *DBusMenuImporter::menu() const
 {
     if (!d->m_menu) {
-        d->m_menu = d->createMenu(0);
+        d->m_menu = d->createMenu(nullptr);
     }
     return d->m_menu;
 }
@@ -383,7 +384,7 @@
 
     QDBusPendingReply<uint, DBusMenuLayoutItem> reply = *watcher;
     if (!reply.isValid()) {
-        qWarning() << reply.error().message();
+        qDebug(DBUSMENUQT) << reply.error().message();
         if (menu) {
             emit menuUpdated(menu);
         }
@@ -396,7 +397,7 @@
     DBusMenuLayoutItem rootItem = reply.argumentAt<1>();
 
     if (!menu) {
-        qWarning() << "No menu for id" << parentId;
+        qDebug(DBUSMENUQT) << "No menu for id" << parentId;
         return;
     }
 
@@ -409,6 +410,7 @@
     for (QAction *action: menu->actions()) {
         int id = action->property(DBUSMENU_PROPERTY_ID).toInt();
         if (! newDBusMenuItemIds.contains(id)) {
+            menu->removeAction(action);
             action->deleteLater();
             d->m_actionForId.remove(id);
         }
@@ -477,6 +479,9 @@
     watcher->setProperty(DBUSMENU_PROPERTY_ID, id);
     connect(watcher, &QDBusPendingCallWatcher::finished, this,
         &DBusMenuImporter::slotAboutToShowDBusCallFinished);
+
+    // Firefox deliberately ignores "aboutToShow" whereas Qt ignores" opened", so we'll just send both all the time...
+    d->sendEvent(id, QStringLiteral("opened"));
 }
 
 void DBusMenuImporter::slotAboutToShowDBusCallFinished(QDBusPendingCallWatcher *watcher)
@@ -491,7 +496,7 @@
 
     QDBusPendingReply<bool> reply = *watcher;
     if (reply.isError()) {
-        qWarning() << "Call to AboutToShow() failed:" << reply.error().message();
+        qDebug(DBUSMENUQT) << "Call to AboutToShow() failed:" << reply.error().message();
         menuUpdated(menu);
         return;
     }
@@ -525,12 +530,6 @@
     Q_ASSERT(menu);
 
     updateMenu(menu);
-
-    QAction *action = menu->menuAction();
-    Q_ASSERT(action);
-
-    int id = action->property(DBUSMENU_PROPERTY_ID).toInt();
-    d->sendEvent(id, QStringLiteral("opened"));
 }
 
 QMenu *DBusMenuImporter::createMenu(QWidget *parent)
diff --git a/plugin/libdbusmenuqt/dbusmenushortcut_p.h b/plugin/libdbusmenuqt/dbusmenushortcut_p.h
--- a/plugin/libdbusmenuqt/dbusmenushortcut_p.h
+++ b/plugin/libdbusmenuqt/dbusmenushortcut_p.h
@@ -22,8 +22,8 @@
 #define DBUSMENUSHORTCUT_H
 
 // Qt
-#include <QtCore/QMetaType>
-#include <QtCore/QStringList>
+#include <QMetaType>
+#include <QStringList>
 
 class QKeySequence;
 
diff --git a/plugin/libdbusmenuqt/dbusmenushortcut_p.cpp b/plugin/libdbusmenuqt/dbusmenushortcut_p.cpp
--- a/plugin/libdbusmenuqt/dbusmenushortcut_p.cpp
+++ b/plugin/libdbusmenuqt/dbusmenushortcut_p.cpp
@@ -21,7 +21,7 @@
 #include "dbusmenushortcut_p.h"
 
 // Qt
-#include <QtGui/QKeySequence>
+#include <QKeySequence>
 
 static const int QT_COLUMN = 0;
 static const int DM_COLUMN = 1;
@@ -41,11 +41,11 @@
       // cf https://bugs.launchpad.net/libdbusmenu-qt/+bug/712565
       {"+", "plus"},
       {"-", "minus"},
-      {0, 0}
+      {nullptr, nullptr}
     };
 
     const Row* ptr = table;
-    for (; ptr->zero != 0; ++ptr) {
+    for (; ptr->zero != nullptr; ++ptr) {
         const char* from = (*ptr)[srcCol];
         const char* to = (*ptr)[dstCol];
         tokens->replaceInStrings(from, to);
diff --git a/plugin/libdbusmenuqt/dbusmenutypes_p.h b/plugin/libdbusmenuqt/dbusmenutypes_p.h
--- a/plugin/libdbusmenuqt/dbusmenutypes_p.h
+++ b/plugin/libdbusmenuqt/dbusmenutypes_p.h
@@ -22,9 +22,9 @@
 #define DBUSMENUTYPES_P_H
 
 // Qt
-#include <QtCore/QList>
-#include <QtCore/QStringList>
-#include <QtCore/QVariant>
+#include <QList>
+#include <QStringList>
+#include <QVariant>
 
 class QDBusArgument;