diff --git a/autotests/test_plugin_effectloader.cpp b/autotests/test_plugin_effectloader.cpp
index 50cb589b84..df6e5f4ebd 100644
--- a/autotests/test_plugin_effectloader.cpp
+++ b/autotests/test_plugin_effectloader.cpp
@@ -58,6 +58,7 @@ private Q_SLOTS:
     void testLoadPluginEffect_data();
     void testLoadPluginEffect();
     void testLoadAllEffects();
+    void testCancelLoadAllEffects();
 };
 
 void TestPluginEffectLoader::testHasEffect_data()
@@ -381,5 +382,32 @@ void TestPluginEffectLoader::testLoadAllEffects()
     spy.clear();
 }
 
+void TestPluginEffectLoader::testCancelLoadAllEffects()
+{
+    // this test verifies that no test gets loaded when the loader gets cleared
+    MockEffectsHandler mockHandler(KWin::OpenGL2Compositing);
+    KWin::PluginEffectLoader loader;
+    loader.setPluginSubDirectory(QString());
+
+    // prepare the configuration to hard enable/disable the effects we want to load
+    KSharedConfig::Ptr config = KSharedConfig::openConfig(QString(), KConfig::SimpleConfig);
+    KConfigGroup plugins = config->group("Plugins");
+    plugins.writeEntry(QStringLiteral("fakeeffectpluginEnabled"), true);
+    plugins.sync();
+
+    loader.setConfig(config);
+
+    qRegisterMetaType<KWin::Effect*>();
+    QSignalSpy spy(&loader, &KWin::PluginEffectLoader::effectLoaded);
+    QVERIFY(spy.isValid());
+
+    loader.queryAndLoadAll();
+    loader.clear();
+
+    // Should not load any effect
+    QVERIFY(!spy.wait(100));
+    QVERIFY(spy.isEmpty());
+}
+
 QTEST_MAIN(TestPluginEffectLoader)
 #include "test_plugin_effectloader.moc"
diff --git a/autotests/test_scripted_effectloader.cpp b/autotests/test_scripted_effectloader.cpp
index 38d77cb2b6..fee8e014c1 100644
--- a/autotests/test_scripted_effectloader.cpp
+++ b/autotests/test_scripted_effectloader.cpp
@@ -72,6 +72,7 @@ private Q_SLOTS:
     void testLoadScriptedEffect_data();
     void testLoadScriptedEffect();
     void testLoadAllEffects();
+    void testCancelLoadAllEffects();
 };
 
 void TestScriptedEffectLoader::testHasEffect_data()
@@ -387,5 +388,32 @@ void TestScriptedEffectLoader::testLoadAllEffects()
     QCOMPARE(loadedEffects.at(1), kwin4 + QStringLiteral("scalein"));
 }
 
+void TestScriptedEffectLoader::testCancelLoadAllEffects()
+{
+    // this test verifies that no test gets loaded when the loader gets cleared
+    MockEffectsHandler mockHandler(KWin::XRenderCompositing);
+    KWin::ScriptedEffectLoader loader;
+
+    // prepare the configuration to hard enable/disable the effects we want to load
+    KSharedConfig::Ptr config = KSharedConfig::openConfig(QString(), KConfig::SimpleConfig);
+    const QString kwin4 = QStringLiteral("kwin4_effect_");
+    KConfigGroup plugins = config->group("Plugins");
+    plugins.writeEntry(kwin4 + QStringLiteral("scaleinEnabled"), true);
+    plugins.sync();
+
+    loader.setConfig(config);
+
+    qRegisterMetaType<KWin::Effect*>();
+    QSignalSpy spy(&loader, &KWin::ScriptedEffectLoader::effectLoaded);
+    QVERIFY(spy.isValid());
+
+    loader.queryAndLoadAll();
+    loader.clear();
+
+    // Should not load any effect
+    QVERIFY(!spy.wait(100));
+    QVERIFY(spy.isEmpty());
+}
+
 QTEST_MAIN(TestScriptedEffectLoader)
 #include "test_scripted_effectloader.moc"
diff --git a/effectloader.cpp b/effectloader.cpp
index ee85ac43e3..030aa21346 100644
--- a/effectloader.cpp
+++ b/effectloader.cpp
@@ -258,9 +258,12 @@ bool ScriptedEffectLoader::loadEffect(const KPluginMetaData &effect, LoadEffectF
 
 void ScriptedEffectLoader::queryAndLoadAll()
 {
+    if (m_queryConnection) {
+        return;
+    }
     // perform querying for the services in a thread
     QFutureWatcher<QList<KPluginMetaData>> *watcher = new QFutureWatcher<QList<KPluginMetaData>>(this);
-    connect(watcher, &QFutureWatcher<QList<KPluginMetaData>>::finished, this,
+    m_queryConnection = connect(watcher, &QFutureWatcher<QList<KPluginMetaData>>::finished, this,
         [this, watcher]() {
             const auto effects = watcher->result();
             for (auto effect : effects) {
@@ -270,6 +273,7 @@ void ScriptedEffectLoader::queryAndLoadAll()
                 }
             }
             watcher->deleteLater();
+            m_queryConnection = QMetaObject::Connection();
         },
         Qt::QueuedConnection);
     watcher->setFuture(QtConcurrent::run(this, &ScriptedEffectLoader::findAllEffects));
@@ -296,7 +300,8 @@ KPluginMetaData ScriptedEffectLoader::findEffect(const QString &name) const
 
 void ScriptedEffectLoader::clear()
 {
-    // TODO: cancel future
+    disconnect(m_queryConnection);
+    m_queryConnection = QMetaObject::Connection();
     m_queue->clear();
 }
 
@@ -432,9 +437,12 @@ bool PluginEffectLoader::loadEffect(const KPluginMetaData &info, LoadEffectFlags
 
 void PluginEffectLoader::queryAndLoadAll()
 {
+    if (m_queryConnection) {
+        return;
+    }
     // perform querying for the services in a thread
     QFutureWatcher<QVector<KPluginMetaData>> *watcher = new QFutureWatcher<QVector<KPluginMetaData>>(this);
-    connect(watcher, &QFutureWatcher<QVector<KPluginMetaData>>::finished, this,
+    m_queryConnection = connect(watcher, &QFutureWatcher<QVector<KPluginMetaData>>::finished, this,
         [this, watcher]() {
             const auto effects = watcher->result();
             for (const auto &effect : effects) {
@@ -444,6 +452,7 @@ void PluginEffectLoader::queryAndLoadAll()
                 }
             }
             watcher->deleteLater();
+            m_queryConnection = QMetaObject::Connection();
         },
         Qt::QueuedConnection);
     watcher->setFuture(QtConcurrent::run(this, &PluginEffectLoader::findAllEffects));
@@ -461,7 +470,8 @@ void PluginEffectLoader::setPluginSubDirectory(const QString &directory)
 
 void PluginEffectLoader::clear()
 {
-    // TODO: cancel future
+    disconnect(m_queryConnection);
+    m_queryConnection = QMetaObject::Connection();
     m_queue->clear();
 }
 
diff --git a/effectloader.h b/effectloader.h
index 38ca86a26a..b33876ad71 100644
--- a/effectloader.h
+++ b/effectloader.h
@@ -323,6 +323,7 @@ private:
     KPluginMetaData findEffect(const QString &name) const;
     QStringList m_loadedEffects;
     EffectLoadQueue< ScriptedEffectLoader, KPluginMetaData > *m_queue;
+    QMetaObject::Connection m_queryConnection;
 };
 
 class PluginEffectLoader : public AbstractEffectLoader
@@ -350,6 +351,7 @@ private:
     QStringList m_loadedEffects;
     EffectLoadQueue< PluginEffectLoader, KPluginMetaData> *m_queue;
     QString m_pluginSubDirectory;
+    QMetaObject::Connection m_queryConnection;
 };
 
 class EffectLoader : public AbstractEffectLoader