-# define PERLVARI(var,type,init) my_perl->var = init;
-# define PERLVARIC(var,type,init) my_perl->var = init;
+# if defined(USE_THREADS)
+# define PERLVARI(var,type,init) PERL_GET_INTERP->var = init;
+# define PERLVARIC(var,type,init) PERL_GET_INTERP->var = init;
+# else /* !USE_THREADS */
+# define PERLVARI(var,type,init) aTHX->var = init;
+# define PERLVARIC(var,type,init) aTHX->var = init;
+# endif /* USE_THREADS */