undefined reference to `Vreen::OAuthConnection::OAuthConnection(int, QObject*'

[themaddoctor]

[ 85%] Linking CXX executable phonefetcher /tmp/cct9CHru.ltrans0.ltrans.o: In function PhoneFetcher::PhoneFetcher(QObject*)': <artificial>:(.text+0x8db): undefined reference to Vreen::OAuthConnection::OAuthConnection(int, QObject*)' collect2: error: ld returned 1 exit status make[2]: *** [examples/cpp/phonefetcher/CMakeFiles/phonefetcher.dir/build.make:162: examples/cpp/phonefetcher/phonefetcher] Error 1 make[1]: *** [CMakeFiles/Makefile2:1002: examples/cpp/phonefetcher/CMakeFiles/phonefetcher.dir/all] Error 2 make: *** [Makefile:141: all] Error 2

Using gcc 7.3 on linux 64-bit