diff --git a/CMakeLists.txt b/CMakeLists.txt
index 561498c..7f31c61 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -150,7 +150,7 @@
 find_package(Threads)
 
 # If this is the root project add longer list of available CMAKE_BUILD_TYPE values
-if(CMAKE_SOURCE_DIR STREQUAL CMAKE_CURRENT_SOURCE_DIR)
+if(NOT MBEDTLS_AS_SUBPROJECT)
     set(CMAKE_BUILD_TYPE ${CMAKE_BUILD_TYPE}
         CACHE STRING "Choose the type of build: None Debug Release Coverage ASan ASanDbg MemSan MemSanDbg Check CheckFull TSan TSanDbg"
         FORCE)