diff --git a/sys/include/net/nanocoap_sock.h b/sys/include/net/nanocoap_sock.h
index ba3e8664aa9f..9bdf41ce2f6c 100644
--- a/sys/include/net/nanocoap_sock.h
+++ b/sys/include/net/nanocoap_sock.h
@@ -229,9 +229,7 @@ typedef struct {
  */
 typedef struct {
     sock_udp_ep_t remote;           /**< remote to send response to         */
-#if defined(MODULE_SOCK_AUX_LOCAL) || DOXYGEN
     sock_udp_ep_t local;            /**< local from which to send response  */
-#endif
     uint8_t token[COAP_TOKEN_LENGTH_MAX];   /**< request token              */
     uint8_t tkl;                    /**< request token length               */
     uint8_t no_response;            /**< no-response bitmap                 */
@@ -246,6 +244,9 @@ typedef struct {
  * The CoAP handler should then respond with an empty ACK by calling
  * @ref coap_build_empty_ack
  *
+ * @warning This function is only available when using the module
+ *          `nanocoap_server_separate`
+ *
  * @param[out]  ctx     Context information for separate response
  * @param[in]   pkt     CoAP packet to which the response will be generated
  * @param[in]   req     Context of the CoAP request
@@ -266,6 +267,11 @@ int nanocoap_server_prepare_separate(nanocoap_server_response_ctx_t *ctx,
  *
  * @pre     @ref nanocoap_server_prepare_separate has been called on @p ctx
  *          inside the CoAP handler
+ * @pre     Synchronization between calls of this function and calls of
+ *          @ref nanocoap_server_prepare_separate is ensured
+ *
+ * @warning This function is only available when using the module
+ *          `nanocoap_server_separate`
  *
  * @param[in]   ctx     Context information for the CoAP response
  * @param[in]   code    CoAP response code
diff --git a/sys/net/application_layer/nanocoap/sock.c b/sys/net/application_layer/nanocoap/sock.c
index c3e16ac24d36..73aa3db89ef5 100644
--- a/sys/net/application_layer/nanocoap/sock.c
+++ b/sys/net/application_layer/nanocoap/sock.c
@@ -1075,6 +1075,7 @@ void auto_init_nanocoap_server(void)
     nanocoap_server_start(&local);
 }
 
+#if MODULE_NANOCOAP_SERVER_SEPARATE
 int nanocoap_server_prepare_separate(nanocoap_server_response_ctx_t *ctx,
                                      coap_pkt_t *pkt, const coap_request_ctx_t *req)
 {
@@ -1092,10 +1093,8 @@ int nanocoap_server_prepare_separate(nanocoap_server_response_ctx_t *ctx,
     ctx->tkl = tkl;
     memcpy(ctx->token, coap_get_token(pkt), tkl);
     memcpy(&ctx->remote, req->remote, sizeof(ctx->remote));
-#ifdef MODULE_SOCK_AUX_LOCAL
     assert(req->local);
     memcpy(&ctx->local, req->local, sizeof(ctx->local));
-#endif
     uint32_t no_response = 0;
     coap_opt_get_uint(pkt, COAP_OPT_NO_RESPONSE, &no_response);
     ctx->no_response = no_response;
@@ -1137,7 +1136,6 @@ int nanocoap_server_send_separate(const nanocoap_server_response_ctx_t *ctx,
     }
 
     sock_udp_aux_tx_t *aux_out_ptr = NULL;
-#ifdef MODULE_SOCK_AUX_LOCAL
     /* make sure we reply with the same address that the request was
      * destined for -- except in the multicast case */
     sock_udp_aux_tx_t aux_out = {
@@ -1147,6 +1145,6 @@ int nanocoap_server_send_separate(const nanocoap_server_response_ctx_t *ctx,
     if (!sock_udp_ep_is_multicast(&ctx->local)) {
         aux_out_ptr = &aux_out;
     }
-#endif
     return sock_udp_sendv_aux(NULL, &head, &ctx->remote, aux_out_ptr);
 }
+#endif