diff --git a/usr.bin/rpcgen/rpc_svcout.c b/usr.bin/rpcgen/rpc_svcout.c
index 20f6aafa7e3f..f90fd0d0ab16 100644
--- a/usr.bin/rpcgen/rpc_svcout.c
+++ b/usr.bin/rpcgen/rpc_svcout.c
@@ -763,9 +763,9 @@ write_msg_out(void)
  
 	if (!Cflag) {
 		f_print(fout, "void _msgout(msg)\n");
-		f_print(fout, "\tchar *msg;\n");
+		f_print(fout, "\tconst char *msg;\n");
 	} else {
-		f_print(fout, "void _msgout(char* msg)\n");
+		f_print(fout, "void _msgout(const char* msg)\n");
 	}
 	f_print(fout, "{\n");
 	f_print(fout, "#ifdef RPC_SVC_FG\n");