diff --git a/libcoap-1.map b/libcoap-1.map
index 831ebc08..4a64503f 100644
--- a/libcoap-1.map
+++ b/libcoap-1.map
@@ -11,6 +11,7 @@ global:
   coap_address_equals;
   coap_add_token;
   coap_adjust_basetime;
+  coap_calc_timeout;
   coap_cancel_all_messages;
   coap_cancel_session_messages;
   coap_can_exit;
diff --git a/libcoap-1.sym b/libcoap-1.sym
index 06e062b0..7fdffd8e 100644
--- a/libcoap-1.sym
+++ b/libcoap-1.sym
@@ -9,6 +9,7 @@ coap_add_resource
 coap_address_equals
 coap_add_token
 coap_adjust_basetime
+coap_calc_timeout
 coap_cancel_all_messages
 coap_cancel_session_messages
 coap_can_exit