diff --git a/src/gui/CMakeLists.txt b/src/gui/CMakeLists.txt
index 8fa22e8..8830628 100644
--- a/src/gui/CMakeLists.txt
+++ b/src/gui/CMakeLists.txt
@@ -14,6 +14,7 @@ find_package(Qt6 COMPONENTS Widgets Network PrintSupport CONFIG REQUIRED)
 
 # For SingleApplication:
 #find_package(Qt5Network CONFIG REQUIRED)
+set(QT_DEFAULT_MAJOR_VERSION 6 CACHE STRING "Qt version to use, defaults to 6")
 set(QAPPLICATION_CLASS QApplication)
 add_compile_definitions(QAPPLICATION_CLASS=${QAPPLICATION_CLASS})