Bug: https://bugs.gentoo.org/883127
Upstream PR: https://github.com/hparra/ruby-serialport/pull/75
--- a/ext/native/posix_serialport_impl.c
+++ b/ext/native/posix_serialport_impl.c
@@ -110,7 +110,7 @@ VALUE sp_create_impl(class, _port)
    struct termios params;
 
    NEWOBJ(sp, struct RFile);
-   OBJSETUP(sp, class, T_FILE);
+   OBJSETUP((VALUE)sp, class, T_FILE);
    MakeOpenFile((VALUE) sp, fp);
 
    switch(TYPE(_port))