portability

diff --git a/skeletons/GeneralizedTime.c b/skeletons/GeneralizedTime.c
index 5e3b9b0..99f2e72 100644
--- a/skeletons/GeneralizedTime.c
+++ b/skeletons/GeneralizedTime.c
@@ -437,7 +437,7 @@
 		if(!opt_gt) { free(buf); return 0; }
 	}
 
-	opt_gt->buf = buf;
+	opt_gt->buf = (unsigned char *)buf;
 	opt_gt->size = size;
 
 	return opt_gt;