CMake has problems with Qt5::Qt5WebEngineWidgets

When running CMake with a small test program for the new Qt5 WebEngine, I get the following error:
Configuring done
CMake Error at CMakeLists.txt:12 (add_executable):
Target "tstEngine" links to target "Qt5::Qt5WebEngineWidgets" but the
target was not found. Perhaps a find_package() call is missing for an
IMPORTED target, or an ALIAS target is missing?

I have included the CMake configuration file, but basically it uses the following:
find_package(Qt5WebEngineWidgets) and
target_link_libraries(${PROJECT_NAME} Qt5::Core Qt5::WebEngineWidgets)

If I remove the engine (only using Qt5Core), everything builds ok.