diff --git a/.ci/Ubuntu22.04/Dockerfile b/.ci/Ubuntu22.04/Dockerfile
index ff2e6e43b..93c8fdea9 100644
--- a/.ci/Ubuntu22.04/Dockerfile
+++ b/.ci/Ubuntu22.04/Dockerfile
@@ -9,20 +9,18 @@ RUN apt-get update && \
         file \
         g++ \
         git \
-        libgl-dev \
         liblzma-dev \
         libmariadb-dev-compat \
         libprotobuf-dev \
-        libqt6multimedia6 \
-        libqt6sql6-mysql \
-        libqt6svg6-dev \
-        libqt6websockets6-dev \
+        libqt5multimedia5-plugins \
+        libqt5sql5-mysql \
+        libqt5svg5-dev \
+        libqt5websockets5-dev \
         ninja-build \
         protobuf-compiler \
-        qt6-image-formats-plugins \
-        qt6-l10n-tools \
-        qt6-multimedia-dev \
-        qt6-tools-dev \
-        qt6-tools-dev-tools \
+        qt5-image-formats-plugins \
+        qtmultimedia5-dev \
+        qttools5-dev \
+        qttools5-dev-tools \
     && apt-get clean \
     && rm -rf /var/lib/apt/lists/*
diff --git a/cmake/FindQtRuntime.cmake b/cmake/FindQtRuntime.cmake
index 42060c835..485affe52 100644
--- a/cmake/FindQtRuntime.cmake
+++ b/cmake/FindQtRuntime.cmake
@@ -42,7 +42,7 @@ list(REMOVE_DUPLICATES REQUIRED_QT_COMPONENTS)
 if(NOT FORCE_USE_QT5)
   # Linguist is now a component in Qt6 instead of an external package
   find_package(
-    Qt6 6.2.3
+    Qt6 6.4.2
     COMPONENTS ${REQUIRED_QT_COMPONENTS} Linguist
     QUIET HINTS ${Qt6_DIR}
   )
diff --git a/cockatrice/src/interface/deck_loader/deck_loader.h b/cockatrice/src/interface/deck_loader/deck_loader.h
index 2530b7f5d..c707c33dc 100644
--- a/cockatrice/src/interface/deck_loader/deck_loader.h
+++ b/cockatrice/src/interface/deck_loader/deck_loader.h
@@ -13,6 +13,7 @@
 #include <QPrinter>
 #include <QTextCursor>
 #include <libcockatrice/deck_list/deck_list.h>
+#include <optional>
 
 inline Q_LOGGING_CATEGORY(DeckLoaderLog, "deck_loader");
 
diff --git a/cockatrice/src/interface/pixel_map_generator.h b/cockatrice/src/interface/pixel_map_generator.h
index 61d771c79..36d1e45f3 100644
--- a/cockatrice/src/interface/pixel_map_generator.h
+++ b/cockatrice/src/interface/pixel_map_generator.h
@@ -12,6 +12,7 @@
 #include <QMap>
 #include <QPixmap>
 #include <libcockatrice/network/server/remote/user_level.h>
+#include <optional>
 
 inline Q_LOGGING_CATEGORY(PixelMapGeneratorLog, "pixel_map_generator");