add const
diff --git a/skeletons/ber_tlv_length.c b/skeletons/ber_tlv_length.c
index 4c2f1e5..47459aa 100644
--- a/skeletons/ber_tlv_length.c
+++ b/skeletons/ber_tlv_length.c
@@ -75,7 +75,7 @@
 }
 
 ssize_t
-ber_skip_length(asn_codec_ctx_t *opt_codec_ctx,
+ber_skip_length(const asn_codec_ctx_t *opt_codec_ctx,
 		int _is_constructed, const void *ptr, size_t size) {
 	ber_tlv_len_t vlen;	/* Length of V in TLV */
 	ssize_t tl;		/* Length of L in TLV */