diff --git a/Tests/RunCMake/CMakeLists.txt b/Tests/RunCMake/CMakeLists.txt
index 67fd65a6fb..e22237660e 100644
--- a/Tests/RunCMake/CMakeLists.txt
+++ b/Tests/RunCMake/CMakeLists.txt
@@ -385,8 +385,9 @@ add_RunCMake_test(CPackConfig)
 add_RunCMake_test(CPackInstallProperties)
 add_RunCMake_test(ExternalProject)
 add_RunCMake_test(FetchContent)
+set(CTestCommandLine_ARGS -DPYTHON_EXECUTABLE=${PYTHON_EXECUTABLE})
 if(NOT CMake_TEST_EXTERNAL_CMAKE)
-  set(CTestCommandLine_ARGS -DTEST_AFFINITY=$<TARGET_FILE:testAffinity>)
+  list(APPEND CTestCommandLine_ARGS -DTEST_AFFINITY=$<TARGET_FILE:testAffinity>)
 endif()
 add_executable(print_stdin print_stdin.c)
 add_RunCMake_test(CTestCommandLine -DTEST_PRINT_STDIN=$<TARGET_FILE:print_stdin>)