diff --git a/python/CMakeLists.txt b/python/CMakeLists.txt
index bd487a9a4c089d91a69cf673c728c59864642b36..d0cd67f9fba2a4c942e6573d642a427d87107d13 100644
--- a/python/CMakeLists.txt
+++ b/python/CMakeLists.txt
@@ -71,8 +71,8 @@ add_subdirectory(test)
 # The module contains the dynamic library, __init__.py and VERSION information.
 set(python_mod_path "${CMAKE_CURRENT_BINARY_DIR}/arbor")
 set_target_properties(pyarb PROPERTIES LIBRARY_OUTPUT_DIRECTORY "${python_mod_path}")
-file(COPY "${CMAKE_SOURCE_DIR}/python/__init__.py" DESTINATION "${python_mod_path}")
-file(COPY "${CMAKE_SOURCE_DIR}/VERSION" DESTINATION "${python_mod_path}")
+file(COPY "${PROJECT_SOURCE_DIR}/python/__init__.py" DESTINATION "${python_mod_path}")
+file(COPY "${PROJECT_SOURCE_DIR}/VERSION" DESTINATION "${python_mod_path}")
 
 # Determine the installation path, according to the Python version.
 # The installation for Python 3.8 would be: