diff -uNr Crypt-GOST-1.00/GOST.xs Crypt-GOST-1.00p/GOST.xs
--- Crypt-GOST-1.00/GOST.xs	2001-05-13 16:11:35.000000000 +0200
+++ Crypt-GOST-1.00p/GOST.xs	2013-08-06 14:36:05.084500779 +0300
@@ -54,7 +54,8 @@
             output = sv_newmortal();
         outlen = 8;
 
-        if (SvREADONLY(output) || !SvUPGRADE(output, SVt_PV))
+        SvUPGRADE(output, SVt_PV);
+        if (SvREADONLY(output))
             croak("cannot use output as lvalue");
 
         gost_crypt(self,