diff --git a/pjsip/include/pjsip/sip_dialog.h b/pjsip/include/pjsip/sip_dialog.h
index da2ec95fb3..dd842677e3 100644
--- a/pjsip/include/pjsip/sip_dialog.h
+++ b/pjsip/include/pjsip/sip_dialog.h
@@ -160,6 +160,7 @@ struct pjsip_dialog
     pj_bool_t           uac_has_2xx;/**< UAC has received 2xx response?     */
     pj_bool_t           secure;     /**< Use secure transport?              */
     pj_bool_t           add_allow;  /**< Add Allow header in requests?      */
+    pj_bool_t           ack_sent;   /**< ACK has been sent?                 */
     pjsip_cid_hdr      *call_id;    /**< Call-ID header.                    */
     pjsip_route_hdr     route_set;  /**< Route set.                         */
     pj_bool_t           route_set_frozen; /**< Route set has been set.      */
diff --git a/pjsip/src/pjsip/sip_dialog.c b/pjsip/src/pjsip/sip_dialog.c
index cda05fbb6e..4a5dd0d14b 100644
--- a/pjsip/src/pjsip/sip_dialog.c
+++ b/pjsip/src/pjsip/sip_dialog.c
@@ -1363,6 +1363,8 @@ PJ_DEF(pj_status_t) pjsip_dlg_send_request( pjsip_dialog *dlg,
         }
 
     } else {
+        dlg->ack_sent = PJ_TRUE;
+
         /* Set transport selector */
         pjsip_tx_data_set_transport(tdata, &dlg->tp_sel);
 
@@ -2079,7 +2081,8 @@ void pjsip_dlg_on_rx_response( pjsip_dialog *dlg, pjsip_rx_data *rdata )
         pj_status_t status;
 
         if (rdata->msg_info.cseq->method.id==PJSIP_INVITE_METHOD &&
-            rdata->msg_info.msg->line.status.code/100 == 2)
+            rdata->msg_info.msg->line.status.code/100 == 2 &&
+            !dlg->ack_sent)
         {
             pjsip_tx_data *ack;
 
diff --git a/pjsip/src/pjsua-lib/pjsua_call.c b/pjsip/src/pjsua-lib/pjsua_call.c
index 4915331696..5587da78e2 100644
--- a/pjsip/src/pjsua-lib/pjsua_call.c
+++ b/pjsip/src/pjsua-lib/pjsua_call.c
@@ -5106,7 +5106,7 @@ pjsip_dialog* on_dlg_forked(pjsip_dialog *dlg, pjsip_rx_data *res)
         res->msg_info.msg->line.status.code/100 == 2)
     {
         pjsip_dialog *forked_dlg;
-        pjsip_tx_data *bye;
+        pjsip_tx_data *bye, *ack;
         pj_status_t status;
 
         /* Create forked dialog */
@@ -5116,6 +5116,12 @@ pjsip_dialog* on_dlg_forked(pjsip_dialog *dlg, pjsip_rx_data *res)
 
         pjsip_dlg_inc_lock(forked_dlg);
 
+        /* Respond with ACK first */
+        status = pjsip_dlg_create_request(forked_dlg, &pjsip_ack_method,
+                                          res->msg_info.cseq->cseq, &ack);
+        if (status == PJ_SUCCESS)
+            pjsip_dlg_send_request(forked_dlg, ack, -1, NULL);
+
         /* Disconnect the call */
         status = pjsip_dlg_create_request(forked_dlg, pjsip_get_bye_method(),
                                           -1, &bye);
diff --git a/tests/pjsua/scripts-sipp/uas-forked-200.xml b/tests/pjsua/scripts-sipp/uas-forked-200.xml
index 2b7a1cb567..ef1da50e78 100644
--- a/tests/pjsua/scripts-sipp/uas-forked-200.xml
+++ b/tests/pjsua/scripts-sipp/uas-forked-200.xml
@@ -97,6 +97,9 @@
     ]]>
   </send>
 
+  <!-- Receive ACK -->
+  <recv request="ACK" optional="false">
+  </recv>
 
   <!-- Receive BYE (for leg 2) -->
   <recv request="BYE" optional="false">
@@ -115,11 +118,6 @@
   </send>
 
 
-  <!-- Receive ACK -->
-  <recv request="ACK" optional="false">
-  </recv>
-
-
   <!-- definition of the response time repartition table (unit is ms)   -->
   <ResponseTimeRepartition value="10, 20, 30, 40, 50, 100, 150, 200"/>