diff --git a/src/python/grpcio/commands.py b/src/python/grpcio/commands.py
index 8240beb2958..d9d23d2b62c 100644
--- a/src/python/grpcio/commands.py
+++ b/src/python/grpcio/commands.py
@@ -217,7 +217,7 @@ class BuildExt(build_ext.build_ext):
             """Test if default compiler is okay with specifying c++ version
             when invoked in C mode. GCC is okay with this, while clang is not.
             """
-            if platform.system() != 'Windows':
+            if platform.system() == 'Windows':
                 return False
             # TODO(lidiz) Remove the generated a.out for success tests.
             cc_test = subprocess.Popen(['cc', '-x', 'c', '-std=c++11', '-'],