diff --git a/kcmkwin/common/effectsmodel.h b/kcmkwin/common/effectsmodel.h
--- a/kcmkwin/common/effectsmodel.h
+++ b/kcmkwin/common/effectsmodel.h
@@ -189,6 +189,11 @@
      */
     void defaults();
 
+    /**
+     * Whether the status of each effect is its default state.
+     */
+    bool isDefaults() const;
+
     /**
      * Whether the model has unsaved changes.
      */
diff --git a/kcmkwin/common/effectsmodel.cpp b/kcmkwin/common/effectsmodel.cpp
--- a/kcmkwin/common/effectsmodel.cpp
+++ b/kcmkwin/common/effectsmodel.cpp
@@ -563,6 +563,19 @@
     }
 }
 
+bool EffectsModel::isDefaults() const
+{
+    return std::all_of(m_effects.constBegin(), m_effects.constEnd(), [](const EffectData &effect) {
+        if (effect.enabledByDefaultFunction && effect.status != Status::EnabledUndeterminded) {
+            return false;
+        }
+        if ((bool)effect.status != effect.enabledByDefault) {
+            return false;
+        }
+        return true;
+    });
+}
+
 bool EffectsModel::needsSave() const
 {
     return std::any_of(m_effects.constBegin(), m_effects.constEnd(),
@@ -647,6 +660,9 @@
     connect(buttons, &QDialogButtonBox::rejected, dialog, &QDialog::reject);
     connect(buttons->button(QDialogButtonBox::RestoreDefaults), &QPushButton::clicked,
         module, &KCModule::defaults);
+    connect(module, &KCModule::defaulted, this, [=](bool defaulted) {
+        buttons->button(QDialogButtonBox::RestoreDefaults)->setEnabled(!defaulted);
+    });
 
     auto layout = new QVBoxLayout(dialog);
     layout->addWidget(module);
diff --git a/kcmkwin/kwineffects/kcm.cpp b/kcmkwin/kwineffects/kcm.cpp
--- a/kcmkwin/kwineffects/kcm.cpp
+++ b/kcmkwin/kwineffects/kcm.cpp
@@ -52,6 +52,7 @@
     setButtons(Apply | Default);
 
     connect(m_model, &EffectsModel::dataChanged, this, &DesktopEffectsKCM::updateNeedsSave);
+    connect(m_model, &EffectsModel::loaded, this, &DesktopEffectsKCM::updateNeedsSave);
 }
 
 DesktopEffectsKCM::~DesktopEffectsKCM()
@@ -115,6 +116,7 @@
 void DesktopEffectsKCM::updateNeedsSave()
 {
     setNeedsSave(m_model->needsSave());
+    setRepresentsDefaults(m_model->isDefaults());
 }
 
 } // namespace KWin