diff --git a/pkg/semtech-loramac/contrib/semtech_loramac.c b/pkg/semtech-loramac/contrib/semtech_loramac.c
index 97c6e5055c..0cd3a46b4f 100644
--- a/pkg/semtech-loramac/contrib/semtech_loramac.c
+++ b/pkg/semtech-loramac/contrib/semtech_loramac.c
@@ -609,7 +609,7 @@ void *_semtech_loramac_event_loop(void *arg)
                 case MSG_TYPE_MAC_TIMEOUT:
                 {
                     DEBUG("[semtech-loramac] MAC timer timeout\n");
-                    void (*callback)(void) = msg.content.ptr;
+                    void (*callback)(void) = (void (*)(void))(uintptr_t)msg.content.value;
                     callback();
                     break;
                 }
diff --git a/pkg/semtech-loramac/contrib/semtech_loramac_timer.c b/pkg/semtech-loramac/contrib/semtech_loramac_timer.c
index c77b24d5b4..d1ed507407 100644
--- a/pkg/semtech-loramac/contrib/semtech_loramac_timer.c
+++ b/pkg/semtech-loramac/contrib/semtech_loramac_timer.c
@@ -44,7 +44,7 @@ void TimerStart(TimerEvent_t *obj)
     xtimer_t *timer = &(obj->dev);
     msg_t *msg = &(obj->msg);
     msg->type = MSG_TYPE_MAC_TIMEOUT;
-    msg->content.ptr = obj->cb;
+    msg->content.value = (uintptr_t)obj->cb;
     xtimer_set_msg(timer, obj->timeout, msg, semtech_loramac_pid);
 }