Project can be built with either Qt 5.15 or Qt 6. ```cmake cmake_minimum_required(VERSION 3.16) project(issue LANGUAGES CXX) find_package(QT NAMES Qt5 Qt6 REQUIRED COMPONENTS Core) find_package(Qt${QT_VERSION_MAJOR} REQUIRED COMPONENTS Widgets) set(CMAKE_AUTOMOC ON) file(GENERATE OUTPUT "widget.h" CONTENT " #ifndef WIDGET_H #define WIDGET_H #include <QWidget> class Widget : public QWidget { Q_OBJECT public: Widget(QWidget *parent = nullptr); }; #endif ") file(GENERATE OUTPUT "widget.cpp" CONTENT " #include \"widget.h\" Widget::Widget(QWidget *parent) : QWidget(parent) {} ") add_library(mylib STATIC ${CMAKE_BINARY_DIR}/widget.cpp ${CMAKE_BINARY_DIR}/widget.h) target_link_libraries(mylib PRIVATE Qt::Widgets) set_source_files_properties(${CMAKE_BINARY_DIR}/widget.cpp ${CMAKE_BINARY_DIR}/widget.h PROPERTIES SKIP_PRECOMPILE_HEADERS ON) target_precompile_headers(mylib PRIVATE [["QWidget"]]) ``` ``` $ mkdir build && cd build && cmake -DCMAKE_PREFIX_PATH=/path/to/Qt .. && ninja ``` Build output ``` makeobj[0]: Entering directory `~/Dev/automoc_no_dep_on_pch/build' ninja: error: 'CMakeFiles/mylib.dir/cmake_pch.hxx.pch', needed by 'CMakeFiles/mylib.dir/mylib_autogen/mocs_compilation.cpp.o', missing and no known rule to make it makeobj[0]: Leaving directory `~/Dev/automoc_no_dep_on_pch/build' ``` Enabling precompiled headers on the target, but excluding all the target sources from using the precompiled header file seemingly causes the generation of the `.pch` file not to happen. And yet AUTOMOC relies on the `.pch` file to exist implicitly, which sounds like a bug. Either it shouldn't depend on the `.pch` file, or it should ensure it is generated.