diff --git a/External/CMakeLists.txt b/External/CMakeLists.txt
index 47f9aaafd..301e48f20 100644
--- a/External/CMakeLists.txt
+++ b/External/CMakeLists.txt
@@ -71,7 +71,8 @@ endif()
 if(ENABLE_OPT AND NOT TARGET SPIRV-Tools-opt)
     if(IS_DIRECTORY ${CMAKE_CURRENT_SOURCE_DIR}/spirv-tools)
         set(SPIRV_SKIP_TESTS ON CACHE BOOL "Skip building SPIRV-Tools tests")
-        add_subdirectory(${CMAKE_CURRENT_SOURCE_DIR}/spirv-tools spirv-tools)
+        # EXCLUDE_FROM_ALL will prevent unneccessary build/installation from spirv-tools
+        add_subdirectory(spirv-tools EXCLUDE_FROM_ALL)
     endif()
 endif()