Guard headers tool.
diff --git a/include/grpc/support/cmdline.h b/include/grpc/support/cmdline.h
index 20de122..c2350a0 100644
--- a/include/grpc/support/cmdline.h
+++ b/include/grpc/support/cmdline.h
@@ -31,8 +31,8 @@
  *
  */
 
-#ifndef __GRPC_SUPPORT_CMDLINE_H__
-#define __GRPC_SUPPORT_CMDLINE_H__
+#ifndef GRPC_SUPPORT_CMDLINE_H
+#define GRPC_SUPPORT_CMDLINE_H
 
 #ifdef __cplusplus
 extern "C" {
@@ -92,4 +92,4 @@
 }
 #endif
 
-#endif /* __GRPC_SUPPORT_CMDLINE_H__ */
+#endif  /* GRPC_SUPPORT_CMDLINE_H */