diff --git a/sycl/CMakeLists.txt b/sycl/CMakeLists.txt
index 13af2ce042ffe..ecf2db32ec5a5 100644
--- a/sycl/CMakeLists.txt
+++ b/sycl/CMakeLists.txt
@@ -147,7 +147,7 @@ function( add_common_options LIB_NAME)
   endif()
 endfunction(add_common_options)
 
-if (LLVM_ENABLE_ASSERTIONS AND NOT SYCL_DISABLE_STL_ASSERTIONS)
+if (LLVM_ENABLE_ASSERTIONS AND NOT SYCL_DISABLE_STL_ASSERTIONS AND NOT WIN32)
   if(SYCL_USE_LIBCXX)
     add_definitions(-D_LIBCPP_DEBUG=1)
     set(SYCL_CLANG_EXTRA_FLAGS "${SYCL_CLANG_EXTRA_FLAGS} -D_LIBCPP_DEBUG=1")
diff --git a/sycl/test/lit.cfg.py b/sycl/test/lit.cfg.py
index 70b09741b2df5..e2134956e9ceb 100644
--- a/sycl/test/lit.cfg.py
+++ b/sycl/test/lit.cfg.py
@@ -35,7 +35,7 @@
 # test_exec_root: The root path where tests should be run.
 config.test_exec_root = os.path.join(config.sycl_obj_root, 'test')
 
-llvm_config.use_clang()
+llvm_config.use_clang(additional_flags=config.sycl_clang_extra_flags.split(' '))
 
 # Propagate some variables from the host environment.
 llvm_config.with_system_environment(['PATH', 'OCL_ICD_FILENAMES', 'SYCL_DEVICE_ALLOWLIST', 'SYCL_CONFIG_FILE_NAME'])
@@ -62,8 +62,6 @@
         config.available_features.add('libcxx')
     llvm_config.with_system_environment('LD_LIBRARY_PATH')
     llvm_config.with_environment('LD_LIBRARY_PATH', config.sycl_libs_dir, append_path=True)
-    llvm_config.with_system_environment('CFLAGS')
-    llvm_config.with_environment('CFLAGS', config.sycl_clang_extra_flags)
 
 elif platform.system() == "Windows":
     config.available_features.add('windows')
diff --git a/sycl/test/on-device/lit.cfg.py b/sycl/test/on-device/lit.cfg.py
index 78a14ff78f846..f42d713ea57eb 100644
--- a/sycl/test/on-device/lit.cfg.py
+++ b/sycl/test/on-device/lit.cfg.py
@@ -35,7 +35,8 @@
 # test_exec_root: The root path where tests should be run.
 config.test_exec_root = os.path.join(config.sycl_obj_root, 'test')
 
-llvm_config.use_clang(use_installed=True)
+llvm_config.use_clang(use_installed=True,
+                      additional_flags=config.sycl_clang_extra_flags.split(' '))
 
 # Propagate some variables from the host environment.
 llvm_config.with_system_environment(['PATH', 'OCL_ICD_FILENAMES', 'SYCL_DEVICE_ALLOWLIST', 'SYCL_CONFIG_FILE_NAME'])
@@ -57,8 +58,6 @@
     config.available_features.add('linux')
     llvm_config.with_system_environment(['LD_LIBRARY_PATH','LIBRARY_PATH','CPATH'])
     llvm_config.with_environment('LD_LIBRARY_PATH', config.sycl_libs_dir, append_path=True)
-    llvm_config.with_system_environment('CFLAGS')
-    llvm_config.with_environment('CFLAGS', config.sycl_clang_extra_flags)
 
 elif platform.system() == "Windows":
     config.available_features.add('windows')