diff --git a/src/controllers/controllerengine.cpp b/src/controllers/controllerengine.cpp
index 473cfc98b91..498b37c1190 100644
--- a/src/controllers/controllerengine.cpp
+++ b/src/controllers/controllerengine.cpp
@@ -1370,10 +1370,10 @@ void ControllerEngine::scratchTick(int deck, int interval) {
     Input:   ID of timer for this deck
     Output:  -
     -------- ------------------------------------------------------ */
-void ControllerEngine::scratchProcess(int timerId) {
-    int deck = m_scratchTimers[timerId];
+void ControllerEngine::scratchProcess(const int timerId) {
+    const int deck = m_scratchTimers[timerId];
     // PlayerManager::groupForDeck is 0-indexed.
-    QString group = PlayerManager::groupForDeck(deck - 1);
+    const QString group = PlayerManager::groupForDeck(deck - 1);
     AlphaBetaFilter* filter = m_scratchFilters[deck];
     if (!filter) {
         qWarning() << "Scratch filter pointer is null on deck" << deck;
@@ -1546,7 +1546,8 @@ void ControllerEngine::softTakeoverIgnoreNextValue(
              rate (optional)
     Output:  -
     -------- ------------------------------------------------------ */
-void ControllerEngine::spinback(int deck, bool activate, double factor, double rate) {
+void ControllerEngine::spinback(
+        const int deck, bool activate, const double factor, const double rate) {
     qDebug() << "   init spinback";
     brake(deck, activate, -factor, rate);
 }
@@ -1557,10 +1558,10 @@ void ControllerEngine::spinback(int deck, bool activate, double factor, double r
              rate (optional, necessary for spinback)
     Output:  -
     -------- ------------------------------------------------------ */
-void ControllerEngine::brake(int deck, bool activate, double factor, double rate) {
+void ControllerEngine::brake(const int deck, bool activate, double factor, const double rate) {
     qDebug() << "   init brake";
     // PlayerManager::groupForDeck is 0-indexed.
-    QString group = PlayerManager::groupForDeck(deck - 1);
+    const QString group = PlayerManager::groupForDeck(deck - 1);
     // enable/disable scratch2 mode
     ControlObjectScript* pScratch2Enable = getControlObjectScript(group, "scratch2_enable");
     if (pScratch2Enable != nullptr) {
@@ -1648,10 +1649,10 @@ void ControllerEngine::brake(int deck, bool activate, double factor, double rate
     Input:   deck, activate/deactivate, factor (optional)
     Output:  -
     -------- ------------------------------------------------------ */
-void ControllerEngine::softStart(int deck, bool activate, double factor) {
+void ControllerEngine::softStart(const int deck, bool activate, double factor) {
     qDebug() << "   init softStart";
     // PlayerManager::groupForDeck is 0-indexed.
-    QString group = PlayerManager::groupForDeck(deck - 1);
+    const QString group = PlayerManager::groupForDeck(deck - 1);
 
     // kill timer when both enabling or disabling
     int timerId = m_scratchTimers.key(deck);
diff --git a/src/controllers/controllerengine.h b/src/controllers/controllerengine.h
index 92e6a9c561f..291e4ce2315 100644
--- a/src/controllers/controllerengine.h
+++ b/src/controllers/controllerengine.h
@@ -132,9 +132,15 @@ class ControllerEngine : public QObject {
     Q_INVOKABLE bool isScratching(int deck);
     Q_INVOKABLE void softTakeover(const QString& group, const QString& name, bool set);
     Q_INVOKABLE void softTakeoverIgnoreNextValue(const QString& group, const QString& name);
-    Q_INVOKABLE void brake(int deck, bool activate, double factor=1.0, double rate=1.0);
-    Q_INVOKABLE void spinback(int deck, bool activate, double factor=1.8, double rate=-10.0);
-    Q_INVOKABLE void softStart(int deck, bool activate, double factor=1.0);
+    Q_INVOKABLE void brake(const int deck,
+            bool activate,
+            double factor = 1.0,
+            const double rate = 1.0);
+    Q_INVOKABLE void spinback(const int deck,
+            bool activate,
+            double factor = 1.8,
+            const double rate = -10.0);
+    Q_INVOKABLE void softStart(const int deck, bool activate, double factor = 1.0);
 
     // Handler for timers that scripts set.
     virtual void timerEvent(QTimerEvent *event);
@@ -192,7 +198,7 @@ class ControllerEngine : public QObject {
     ControlObjectScript* getControlObjectScript(const QString& group, const QString& name);
 
     // Scratching functions & variables
-    void scratchProcess(int timerId);
+    void scratchProcess(const int timerId);
     void stopScratchTimer(const int timerId);
 
     bool isDeckPlaying(const QString& group);