diff --git a/src/mixer/playermanager.h b/src/mixer/playermanager.h
index 602cfb13a390..95ef7bfb1735 100644
--- a/src/mixer/playermanager.h
+++ b/src/mixer/playermanager.h
@@ -32,7 +32,7 @@ class PlayerManagerInterface {
     virtual ~PlayerManagerInterface() = default;
 
     // Get a BaseTrackPlayer (i.e. a Deck or a Sampler) by its group
-    virtual BaseTrackPlayer* getPlayer(const QString group) const = 0;
+    virtual BaseTrackPlayer* getPlayer(const QString& group) const = 0;
     virtual BaseTrackPlayer* getPlayer(const ChannelHandle& channelHandle) const = 0;
 
     // Get the deck by its deck number. Decks are numbered starting with 1.
diff --git a/src/test/signalpathtest.h b/src/test/signalpathtest.h
index e09e52269bbf..56aef9ed6b10 100644
--- a/src/test/signalpathtest.h
+++ b/src/test/signalpathtest.h
@@ -66,7 +66,7 @@ class BaseSignalPathTest : public MixxxTest {
                                                m_pEffectsManager, m_pChannelHandleFactory,
                                                false);
 
-        m_pMixerDeck1 = new Deck(NULL,
+        m_pMixerDeck1 = new Deck(nullptr,
                 m_pConfig,
                 m_pEngineMaster,
                 m_pEffectsManager,
@@ -91,7 +91,7 @@ class BaseSignalPathTest : public MixxxTest {
         m_pChannel1 = m_pMixerDeck1->getEngineDeck();
         m_pChannel2 = m_pMixerDeck2->getEngineDeck();
         m_pChannel3 = m_pMixerDeck3->getEngineDeck();
-        m_pPreview1 = new PreviewDeck(NULL,
+        m_pPreview1 = new PreviewDeck(nullptr,
                 m_pConfig,
                 m_pEngineMaster,
                 m_pEffectsManager,