diff --git a/src/python/grpcio/_parallel_compile_patch.py b/src/python/grpcio/_parallel_compile_patch.py
index 4d03ef49ba0..b34aa17fd0b 100644
--- a/src/python/grpcio/_parallel_compile_patch.py
+++ b/src/python/grpcio/_parallel_compile_patch.py
@@ -40,7 +40,7 @@ def _parallel_compile(self,
     # setup the same way as distutils.ccompiler.CCompiler
     # https://github.com/python/cpython/blob/31368a4f0e531c19affe2a1becd25fc316bc7501/Lib/distutils/ccompiler.py#L564
     macros, objects, extra_postargs, pp_opts, build = self._setup_compile(
-        output_dir, macros, include_dirs, sources, depends, extra_postargs)
+        str(output_dir), macros, include_dirs, sources, depends, extra_postargs)
     cc_args = self._get_cc_args(pp_opts, debug, extra_preargs)
 
     def _compile_single_file(obj):