diff --git a/ssl/internal.h b/ssl/internal.h
index 67cf5b0..8f68fc5 100644
--- a/ssl/internal.h
+++ b/ssl/internal.h
@@ -3513,7 +3513,7 @@
   bssl::UniquePtr<bssl::CERT> cert;
 
   // callback that allows applications to peek at protocol messages
-  void (*msg_callback)(int write_p, int version, int content_type,
+  void (*msg_callback)(int is_write, int version, int content_type,
                        const void *buf, size_t len, SSL *ssl,
                        void *arg) = nullptr;
   void *msg_callback_arg = nullptr;