diff --git a/library/oid.c b/library/oid.c
index f37bbf6..1aaf8e8 100644
--- a/library/oid.c
+++ b/library/oid.c
@@ -369,6 +369,7 @@
 FN_OID_TYPED_FROM_ASN1(oid_pk_alg_t, pk_alg, oid_pk_alg);
 FN_OID_GET_ATTR1(oid_get_pk_alg, oid_pk_alg_t, pk_alg, pk_type_t, pk_alg);
 
+#if defined(POLARSSL_ECP_C)
 /*
  * For namedCurve (RFC 5480)
  */
@@ -407,6 +408,8 @@
 
 FN_OID_TYPED_FROM_ASN1(oid_ecp_grp_t, grp_id, oid_ecp_grp);
 FN_OID_GET_ATTR1(oid_get_ec_grp, oid_ecp_grp_t, grp_id, ecp_group_id, grp_id);
+FN_OID_GET_OID_BY_ATTR1(oid_get_oid_by_ec_grp, oid_ecp_grp_t, oid_ecp_grp, ecp_group_id, grp_id);
+#endif /* POLARSSL_ECP_C */
 
 #if defined(POLARSSL_CIPHER_C)
 /*