Yes, the library is a static library included in the repository (compiled with -fPIC). The README in the linked repository includes a link to the repository for just the library. I changed the Makefile to have set(CMAKE_AUTOMOC ON) set(THREADS_PREFER_PTHREAD_FLAG ON) find_package(Threads REQUIRED) include_directories(${CMAKE_SOURCE_DIR}/plugins/SockTalkFrontend/lib) link_directories(${CMAKE_SOURCE_DIR}/plugins/SockTalkFrontend/lib) add_library(${PLUGIN} MODULE ${SRC}) target_link_libraries(${PLUGIN} ${CMAKE_SOURCE_DIR}/plugins/SockTalkFrontend/lib/libsocktalk.a Threads::Threads) set_target_properties(${PLUGIN} PROPERTIES LIBRARY_OUTPUT_DIRECTORY ${PLUGIN}) qt5_use_modules(${PLUGIN} Qml Quick DBus) But it didn't change the outcome. Thanks for the tip of linking multiple libraries in the same call though.