add const
diff --git a/skeletons/constr_CHOICE_oer.c b/skeletons/constr_CHOICE_oer.c
index 6cd7a0a..4319fde 100644
--- a/skeletons/constr_CHOICE_oer.c
+++ b/skeletons/constr_CHOICE_oer.c
@@ -125,7 +125,7 @@
 }
 
 asn_dec_rval_t
-CHOICE_decode_oer(asn_codec_ctx_t *opt_codec_ctx, asn_TYPE_descriptor_t *td,
+CHOICE_decode_oer(const asn_codec_ctx_t *opt_codec_ctx, asn_TYPE_descriptor_t *td,
                   const asn_oer_constraints_t *constraints, void **struct_ptr,
                   const void *ptr, size_t size) {
     /*