diff --git a/tools/distrib/python/grpcio_tools/grpc_tools/command.py b/tools/distrib/python/grpcio_tools/grpc_tools/command.py
index 7ede05f1404..93503c4cc36 100644
--- a/tools/distrib/python/grpcio_tools/grpc_tools/command.py
+++ b/tools/distrib/python/grpcio_tools/grpc_tools/command.py
@@ -42,7 +42,7 @@ def build_package_protos(package_root):
             '--grpc_python_out={}'.format(inclusion_root),
         ] + [proto_file]
         if protoc.main(command) != 0:
-            sys.stderr.write('warning: {} failed'.format(command))
+            raise RuntimeError('error: {} failed'.format(command))
 
 
 class BuildPackageProtos(setuptools.Command):