diff -ur source.orig/pjsip/src/pjsip-ua/sip_timer.c source/pjsip/src/pjsip-ua/sip_timer.c
--- source.orig/pjsip/src/pjsip-ua/sip_timer.c	2018-06-19 12:00:33.000000000 +0200
+++ source/pjsip/src/pjsip-ua/sip_timer.c	2020-06-30 15:55:51.501891714 +0200
@@ -412,7 +412,7 @@
 		status = pjmedia_sdp_neg_get_neg_local(inv->neg, &offer);
 	    if (status == PJ_SUCCESS) {
 		status = pjsip_create_sdp_body(tdata->pool, 
-					(pjmedia_sdp_session*)offer, &body);
+					pjmedia_sdp_session_clone(tdata->pool, offer), &body);
 		tdata->msg->body = body;
 	    }
 	}