diff --git a/.github/workflows/desktop-build.yml b/.github/workflows/desktop-build.yml
index 8efe8bfb..5ccf2462 100644
--- a/.github/workflows/desktop-build.yml
+++ b/.github/workflows/desktop-build.yml
@@ -201,7 +201,7 @@ jobs:
           - target: Debug # tests only
             os: macos-latest
             xcode: 14.2
-            qt_version: 6.*
+            qt_version: 6.5
             qt_modules: "qtmultimedia qtwebsockets"
             type: Debug
             do_tests: 1
@@ -251,7 +251,8 @@ jobs:
           install_qt: ${{matrix.qt_version}}
         run: |
           brew update
-          brew install protobuf
+          brew install protobuf@21
+          brew link --force protobuf@21
           if [[ $install_qt == homebrew ]]; then
             brew install qt --force-bottle
           else # for some reason the tests fail with the action installed qt?
diff --git a/CMakeLists.txt b/CMakeLists.txt
index a278ee0a..f151b5fd 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -179,7 +179,7 @@ else()
   # other: osx/llvm, bsd/llvm
   set(CMAKE_CXX_FLAGS_RELEASE "-O2")
   if(WARNING_AS_ERROR)
-    set(CMAKE_CXX_FLAGS_DEBUG "-g -O0 -Wall -Wextra -Werror")
+    set(CMAKE_CXX_FLAGS_DEBUG "-g -O0 -Wall -Wextra -Werror -Wno-unused-parameter")
   else()
     set(CMAKE_CXX_FLAGS_DEBUG "-g -O0 -Wall -Wextra")
   endif()
diff --git a/cockatrice/src/abstractcarddragitem.h b/cockatrice/src/abstractcarddragitem.h
index 4f379e87..682c2a6b 100644
--- a/cockatrice/src/abstractcarddragitem.h
+++ b/cockatrice/src/abstractcarddragitem.h
@@ -21,18 +21,18 @@ public:
     {
         Type = typeCardDrag
     };
-    int type() const
+    int type() const override
     {
         return Type;
     }
     AbstractCardDragItem(AbstractCardItem *_item, const QPointF &_hotSpot, AbstractCardDragItem *parentDrag = 0);
     ~AbstractCardDragItem();
-    QRectF boundingRect() const
+    QRectF boundingRect() const override
     {
         return QRectF(0, 0, CARD_WIDTH, CARD_HEIGHT);
     }
     QPainterPath shape() const override;
-    void paint(QPainter *painter, const QStyleOptionGraphicsItem *option, QWidget *widget);
+    void paint(QPainter *painter, const QStyleOptionGraphicsItem *option, QWidget *widget) override;
     AbstractCardItem *getItem() const
     {
         return item;
@@ -45,7 +45,7 @@ public:
     virtual void updatePosition(const QPointF &cursorScenePos) = 0;
 
 protected:
-    void mouseMoveEvent(QGraphicsSceneMouseEvent *event);
+    void mouseMoveEvent(QGraphicsSceneMouseEvent *event) override;
 };
 
 #endif
diff --git a/cockatrice/src/abstractcarditem.h b/cockatrice/src/abstractcarditem.h
index 7800eb8f..98ef4d1a 100644
--- a/cockatrice/src/abstractcarditem.h
+++ b/cockatrice/src/abstractcarditem.h
@@ -44,7 +44,7 @@ public:
     {
         Type = typeCard
     };
-    int type() const
+    int type() const override
     {
         return Type;
     }
@@ -53,11 +53,11 @@ public:
                      int _id = -1,
                      QGraphicsItem *parent = nullptr);
     ~AbstractCardItem();
-    QRectF boundingRect() const;
+    QRectF boundingRect() const override;
     QPainterPath shape() const override;
     QSizeF getTranslatedSize(QPainter *painter) const;
     void paintPicture(QPainter *painter, const QSizeF &translatedSize, int angle);
-    void paint(QPainter *painter, const QStyleOptionGraphicsItem *option, QWidget *widget);
+    void paint(QPainter *painter, const QStyleOptionGraphicsItem *option, QWidget *widget) override;
     CardInfoPtr getInfo() const
     {
         return info;
@@ -104,9 +104,9 @@ public:
 
 protected:
     void transformPainter(QPainter *painter, const QSizeF &translatedSize, int angle);
-    void mousePressEvent(QGraphicsSceneMouseEvent *event);
-    void mouseReleaseEvent(QGraphicsSceneMouseEvent *event);
-    QVariant itemChange(QGraphicsItem::GraphicsItemChange change, const QVariant &value);
+    void mousePressEvent(QGraphicsSceneMouseEvent *event) override;
+    void mouseReleaseEvent(QGraphicsSceneMouseEvent *event) override;
+    QVariant itemChange(QGraphicsItem::GraphicsItemChange change, const QVariant &value) override;
     void cacheBgColor();
 };
 
diff --git a/cockatrice/src/pilezone.h b/cockatrice/src/pilezone.h
index 9c2e5cd3..6e405b6b 100644
--- a/cockatrice/src/pilezone.h
+++ b/cockatrice/src/pilezone.h
@@ -18,18 +18,18 @@ public:
              bool _isShufflable,
              bool _contentsKnown,
              QGraphicsItem *parent = nullptr);
-    QRectF boundingRect() const;
+    QRectF boundingRect() const override;
     QPainterPath shape() const override;
-    void paint(QPainter *painter, const QStyleOptionGraphicsItem *option, QWidget *widget);
-    void reorganizeCards();
-    void handleDropEvent(const QList<CardDragItem *> &dragItems, CardZone *startZone, const QPoint &dropPoint);
+    void paint(QPainter *painter, const QStyleOptionGraphicsItem *option, QWidget *widget) override;
+    void reorganizeCards() override;
+    void handleDropEvent(const QList<CardDragItem *> &dragItems, CardZone *startZone, const QPoint &dropPoint) override;
 
 protected:
-    void mousePressEvent(QGraphicsSceneMouseEvent *event);
-    void mouseMoveEvent(QGraphicsSceneMouseEvent *event);
-    void mouseReleaseEvent(QGraphicsSceneMouseEvent *event);
-    void hoverEnterEvent(QGraphicsSceneHoverEvent *event);
-    void addCardImpl(CardItem *card, int x, int y);
+    void mousePressEvent(QGraphicsSceneMouseEvent *event) override;
+    void mouseMoveEvent(QGraphicsSceneMouseEvent *event) override;
+    void mouseReleaseEvent(QGraphicsSceneMouseEvent *event) override;
+    void hoverEnterEvent(QGraphicsSceneHoverEvent *event) override;
+    void addCardImpl(CardItem *card, int x, int y) override;
 };
 
 #endif
diff --git a/cockatrice/src/releasechannel.cpp b/cockatrice/src/releasechannel.cpp
index 095c4900..31a26818 100644
--- a/cockatrice/src/releasechannel.cpp
+++ b/cockatrice/src/releasechannel.cpp
@@ -42,7 +42,7 @@ void ReleaseChannel::checkForUpdates()
 }
 
 // Different release channel checking functions for different operating systems
-#if defined(Q_OS_OSX)
+#if defined(Q_OS_MACOS)
 bool ReleaseChannel::downloadMatchesCurrentOS(const QString &fileName)
 {
     static QRegularExpression version_regex("macOS-(\\d+)\\.(\\d+)");
diff --git a/common/room_message_type.h b/common/room_message_type.h
index 4e87bd86..7b7ad9ac 100644
--- a/common/room_message_type.h
+++ b/common/room_message_type.h
@@ -1,7 +1,7 @@
 #ifndef ROOM_MESSAGE_TYPE_H
 #define ROOM_MESSAGE_TYPE_H
 
-#ifdef Q_OS_OSX
+#ifdef Q_OS_MACOS
 // avoid collision from Mac OS X's ConditionalMacros.h
 // https://github.com/protocolbuffers/protobuf/issues/119
 #undef TYPE_BOOL
diff --git a/common/user_level.h b/common/user_level.h
index c682a93b..5d720c0a 100644
--- a/common/user_level.h
+++ b/common/user_level.h
@@ -1,7 +1,7 @@
 #ifndef USER_LEVEL_H
 #define USER_LEVEL_H
 
-#ifdef Q_OS_OSX
+#ifdef Q_OS_MACOS
 // avoid collision from Mac OS X's ConditionalMacros.h
 // https://github.com/protocolbuffers/protobuf/issues/119
 #undef TYPE_BOOL