diff --git a/skeletons/oer_encoder.c b/skeletons/oer_encoder.c
index 4358a92..490043c 100644
--- a/skeletons/oer_encoder.c
+++ b/skeletons/oer_encoder.c
@@ -47,7 +47,7 @@
  */
 asn_enc_rval_t
 oer_encode_to_buffer(struct asn_TYPE_descriptor_s *type_descriptor,
-                     asn_oer_constraints_t *constraints,
+                     const asn_oer_constraints_t *constraints,
                      void *struct_ptr,  /* Structure to be encoded */
                      void *buffer,      /* Pre-allocated buffer */
                      size_t buffer_size /* Initial buffer size (maximum) */