diff -wbBur Crypt-DES-2.05.org/DES.xs Crypt-DES-2.05/DES.xs
--- Crypt-DES-2.05.org/DES.xs	2005-12-08 18:52:50.000000000 +0300
+++ Crypt-DES-2.05/DES.xs	2013-05-20 15:35:58.668612530 +0400
@@ -64,8 +64,7 @@
 			output = sv_newmortal();
 		output_len = 8;
 
-		if (!SvUPGRADE(output, SVt_PV))
-			croak("cannot use output argument as lvalue");
+		SvUPGRADE(output, SVt_PV);
 
 		perl_des_crypt(input, SvGROW(output, output_len), (i32 *)ks, enc_flag);