diff --git a/clang-tools-extra/clangd/test/CMakeLists.txt b/clang-tools-extra/clangd/test/CMakeLists.txt
--- a/clang-tools-extra/clangd/test/CMakeLists.txt
+++ b/clang-tools-extra/clangd/test/CMakeLists.txt
@@ -29,7 +29,10 @@
 
 configure_lit_site_cfg(
   ${CMAKE_CURRENT_SOURCE_DIR}/lit.site.cfg.py.in
-  ${CMAKE_CURRENT_BINARY_DIR}/lit.site.cfg.py)
+  ${CMAKE_CURRENT_BINARY_DIR}/lit.site.cfg.py
+  MAIN_CONFIG
+  ${CMAKE_CURRENT_SOURCE_DIR}/lit.cfg.py
+  )
 
 add_lit_testsuite(check-clangd "Running the Clangd regression tests"
   ${CMAKE_CURRENT_BINARY_DIR}/../unittests;${CMAKE_CURRENT_BINARY_DIR}