Configure: -system-freetype fails

../src/configure -system-freetype
opt: freetype val: system
Overriding option 'freetype' with 'system' (was: 'undefined')
'/snap/cmake/619/bin/cmake' '-DINPUT_freetype=system' '-G' 'Ninja' '/home/kakoehne/dev/qt/dev/src'
[...]
-- Found WrapSystemFreetype: /usr/lib/x86_64-linux-gnu/libfreetype.so (found suitable version "2.8.1", minimum required is "2.2.0") 
[...]
CMake Error at qtbase/cmake/QtFeature.cmake:194 (message):
  Sanity check failed: FEATURE_freetype has invalid value "system"!
Call Stack (most recent call first):
  qtbase/cmake/QtFeature.cmake:284 (qt_feature_set_cache_value)
  qtbase/cmake/QtFeature.cmake:471 (qt_evaluate_feature)
  qtbase/cmake/QtFeature.cmake:451 (qt_feature_module_end)
  qtbase/src/CMakeLists.txt:12 (qt_feature_evaluate_features)


-- Configuring incomplete, errors occurred!
See also "/home/kakoehne/dev/qt/dev/build/CMakeFiles/CMakeOutput.log".
See also "/home/kakoehne/dev/qt/dev/build/CMakeFiles/CMakeError.log".
CMake Error at /home/kakoehne/dev/qt/dev/src/qtbase/cmake/QtProcessConfigureArgs.cmake:751 (message):
  CMake exited with code 1.