Fix include guard
diff --git a/include/grpcpp/support/error_details_impl.h b/include/grpcpp/support/error_details_impl.h
index daa630c..ae5f04c 100644
--- a/include/grpcpp/support/error_details_impl.h
+++ b/include/grpcpp/support/error_details_impl.h
@@ -16,7 +16,7 @@
  *
  */
 
-#ifndef GRPCPP_SUPPORT_ERROR_DETAILS__IMPL_H
+#ifndef GRPCPP_SUPPORT_ERROR_DETAILS_IMPL_H
 #define GRPCPP_SUPPORT_ERROR_DETAILS_IMPL_H
 
 #include <grpcpp/support/status.h>