diff --git a/python/CMakeLists.txt b/python/CMakeLists.txt
index 98bbe66650..f7228de0a1 100644
--- a/python/CMakeLists.txt
+++ b/python/CMakeLists.txt
@@ -105,7 +105,7 @@ if (BUILD_TESTING)
     endif()
 
     set(_env_vars)
-    list(APPEND _env_vars "PYTHONPATH=${CMAKE_INSTALL_PREFIX}/${CMAKE_INSTALL_LIBDIR}/python/")
+    list(APPEND _env_vars "PYTHONPATH=${CMAKE_INSTALL_PREFIX}/${CMAKE_INSTALL_LIBDIR}/python/:$ENV{PYTHONPATH}")
     list(APPEND _env_vars "LD_LIBRARY_PATH=${CMAKE_INSTALL_PREFIX}/${CMAKE_INSTALL_LIBDIR}:$ENV{LD_LIBRARY_PATH}")
     set_tests_properties(${test} PROPERTIES
       ENVIRONMENT "${_env_vars}")
diff --git a/test/integration/CMakeLists.txt b/test/integration/CMakeLists.txt
index da422d2a89..df28287316 100644
--- a/test/integration/CMakeLists.txt
+++ b/test/integration/CMakeLists.txt
@@ -246,5 +246,5 @@ endif()
 
 if (TARGET INTEGRATION_python_system_loader)
   set_tests_properties(INTEGRATION_python_system_loader PROPERTIES
-    ENVIRONMENT "PYTHONPATH=${CMAKE_INSTALL_PREFIX}/${CMAKE_INSTALL_LIBDIR}/python/")
+    ENVIRONMENT "PYTHONPATH=${CMAKE_INSTALL_PREFIX}/${CMAKE_INSTALL_LIBDIR}/python/:$ENV{PYTHONPATH}")
 endif()