diff --git a/lib/call-session.js b/lib/call-session.js
index 610a4e8..79fddbf 100644
--- a/lib/call-session.js
+++ b/lib/call-session.js
@@ -148,128 +148,137 @@ class CallSession extends Emitter {
     else uri = `${obj.scheme}:${host}`;
     this.logger.info(`uri will be: ${uri}, proxy ${proxy}`);
 
-    try {
-      const opts = {
-        ...this.rtpEngineOpts.common,
-        ...this.rtpEngineOpts.uac.mediaOpts,
-        'from-tag': this.rtpEngineOpts.uas.tag,
-        direction:  ['public', 'private'],
-        sdp
-      };
-      const startAt = process.hrtime();
-      const response = await this.offer(opts);
-      this.rtpengineIp = opts.sdp ? parseConnectionIp(opts.sdp) : 'undefined';
-      const rtt = roundTripTime(startAt);
-      this.stats.histogram('app.rtpengine.response_time', rtt, [
-        'direction:inbound', 'command:offer', `rtpengine:${this.rtpengineIp}`]);
-      this.logger.debug({opts, response, rtt, rtpengine: this.rtpengineIp}, 'response from rtpengine to offer');
-      if ('ok' !== response.result) {
-        this.logger.error({}, `rtpengine offer failed with ${JSON.stringify(response)}`);
-        throw new Error('rtpengine failed: answer');
-      }
-
-      let headers = {
-        'From': createBLegFromHeader(this.req),
-        'To': this.req.get('To'),
-        'X-Account-Sid': this.req.locals.account_sid,
-        'X-CID': this.req.get('Call-ID'),
-        'X-Forwarded-For': `${this.req.source_address}`
-      };
-      if (this.privateSipAddress) headers = {...headers, Contact: `<sip:${this.privateSipAddress}>`};
-
-      const spdOfferB = this.siprec && this.xml ?
-        createSiprecBody(headers, response.sdp, this.xml.type, this.xml.content) :
-        response.sdp;
-
-      const responseHeaders = {};
-      if (this.req.locals.carrier) {
-        Object.assign(headers, {
-          'X-Originating-Carrier': this.req.locals.carrier,
-          'X-Voip-Carrier-Sid': this.req.locals.voip_carrier_sid
-        });
-      }
-      if (this.req.locals.msTeamsTenantFqdn) {
-        Object.assign(headers, {'X-MS-Teams-Tenant-FQDN': this.req.locals.msTeamsTenantFqdn});
-
-        // for Microsoft Teams the Contact header must include the tenant FQDN
-        Object.assign(responseHeaders, {
-          Allow: 'INVITE, ACK, OPTIONS, CANCEL, BYE, NOTIFY, UPDATE, PRACK',
-          Contact: `sip:${this.req.locals.msTeamsTenantFqdn}`
-        });
-      }
-      if (this.req.locals.application_sid) {
-        Object.assign(headers, {'X-Application-Sid': this.req.locals.application_sid});
-      }
-      else if (this.req.authorization) {
-        if (this.req.authorization.grant && this.req.authorization.grant.application_sid) {
-          Object.assign(headers, {'X-Application-Sid': this.req.authorization.grant.application_sid});
+    const opts = {
+      ...this.rtpEngineOpts.common,
+      ...this.rtpEngineOpts.uac.mediaOpts,
+      'from-tag': this.rtpEngineOpts.uas.tag,
+      direction:  ['public', 'private'],
+      sdp
+    };
+    const startAt = process.hrtime();
+    this.offer(opts, async(err, response) => {
+      try {
+        if (err || 'ok' !== response.result) {
+          this.logger.error({}, `rtpengine offer failed with ${JSON.stringify(response)}`);
+          return this.res.send(480, {
+            headers: {
+              'X-Reason': 'RTPENGINE_OFFER_FAILED'
+            }
+          });
         }
-        if (this.req.authorization.challengeResponse) {
-          const {username, realm} = this.req.authorization.challengeResponse;
-          Object.assign(headers, {'X-Authenticated-User': `${username}@${realm}`});
+        this.rtpengineIp = opts.sdp ? parseConnectionIp(opts.sdp) : 'undefined';
+        const rtt = roundTripTime(startAt);
+        this.stats.histogram('app.rtpengine.response_time', rtt, [
+          'direction:inbound', 'command:offer', `rtpengine:${this.rtpengineIp}`]);
+        this.logger.debug({opts, response, rtt, rtpengine: this.rtpengineIp}, 'response from rtpengine to offer');
+        if ('ok' !== response.result) {
         }
-      }
+        let headers = {
+          'From': createBLegFromHeader(this.req),
+          'To': this.req.get('To'),
+          'X-Account-Sid': this.req.locals.account_sid,
+          'X-CID': this.req.get('Call-ID'),
+          'X-Forwarded-For': `${this.req.source_address}`
+        };
+        if (this.privateSipAddress) headers = {...headers, Contact: `<sip:${this.privateSipAddress}>`};
 
-      if (this.req.canceled) throw new Error('call canceled');
+        const spdOfferB = this.siprec && this.xml ?
+          createSiprecBody(headers, response.sdp, this.xml.type, this.xml.content) :
+          response.sdp;
 
-      // now send the INVITE in towards the feature servers
-      debug(`sending INVITE to ${proxy} with ${uri}`);
-      const {uas, uac} = await this.srf.createB2BUA(this.req, this.res, uri, {
-        proxy,
-        headers,
-        responseHeaders,
-        proxyRequestHeaders: [
-          'all',
-          '-Authorization',
-          '-Max-Forwards',
-          '-Record-Route',
-          '-Session-Expires',
-          '-X-Subspace-Forwarded-For'
-        ],
-        proxyResponseHeaders: ['all', '-X-Trace-ID'],
-        localSdpB: spdOfferB,
-        localSdpA: async(sdp, res) => {
-          this.rtpEngineOpts.uac.tag = res.getParsedHeader('To').params.tag;
-          const opts = {
-            ...this.rtpEngineOpts.common,
-            ...this.rtpEngineOpts.uas.mediaOpts,
-            'from-tag': this.rtpEngineOpts.uas.tag,
-            'to-tag': this.rtpEngineOpts.uac.tag,
-            sdp
-          };
-          const startAt = process.hrtime();
-          const response = await this.answer(opts);
-          const rtt = roundTripTime(startAt);
-          this.stats.histogram('app.rtpengine.response_time', rtt, [
-            'direction:inbound', 'command:answer', `rtpengine:${this.rtpengineIp}`]);
-          if ('ok' !== response.result) {
-            this.logger.error(`rtpengine answer failed with ${JSON.stringify(response)}`);
-            throw new Error('rtpengine failed: answer');
+        const responseHeaders = {};
+        if (this.req.locals.carrier) {
+          Object.assign(headers, {
+            'X-Originating-Carrier': this.req.locals.carrier,
+            'X-Voip-Carrier-Sid': this.req.locals.voip_carrier_sid
+          });
+        }
+        if (this.req.locals.msTeamsTenantFqdn) {
+          Object.assign(headers, {'X-MS-Teams-Tenant-FQDN': this.req.locals.msTeamsTenantFqdn});
+
+          // for Microsoft Teams the Contact header must include the tenant FQDN
+          Object.assign(responseHeaders, {
+            Allow: 'INVITE, ACK, OPTIONS, CANCEL, BYE, NOTIFY, UPDATE, PRACK',
+            Contact: `sip:${this.req.locals.msTeamsTenantFqdn}`
+          });
+        }
+        if (this.req.locals.application_sid) {
+          Object.assign(headers, {'X-Application-Sid': this.req.locals.application_sid});
+        }
+        else if (this.req.authorization) {
+          if (this.req.authorization.grant && this.req.authorization.grant.application_sid) {
+            Object.assign(headers, {'X-Application-Sid': this.req.authorization.grant.application_sid});
+          }
+          if (this.req.authorization.challengeResponse) {
+            const {username, realm} = this.req.authorization.challengeResponse;
+            Object.assign(headers, {'X-Authenticated-User': `${username}@${realm}`});
           }
-          return response.sdp;
         }
-      });
 
-      // successfully connected
-      this.logger.info('call connected successfully to feature server');
-      debug('call connected successfully to feature server');
-      this._setHandlers({uas, uac});
-      return;
-    } catch (err) {
-      this.rtpEngineResource.destroy().catch((err) => this.logger.info({err}, 'Error destroying rtpe after failure'));
-      this.activeCallIds.delete(this.req.get('Call-ID'));
-      this.stats.gauge('sbc.sip.calls.count', this.activeCallIds.size);
-      if (err instanceof SipError) {
-        const tags = ['accepted:no', `sipStatus:${err.status}`, `originator:${this.req.locals.originator}`];
-        this.stats.increment('sbc.terminations', tags);
-        this.logger.info(`call failed to connect to feature server with ${err.status}`);
-        this.emit('failed');
+        if (this.req.canceled) throw new Error('call canceled');
+
+        // now send the INVITE in towards the feature servers
+        debug(`sending INVITE to ${proxy} with ${uri}`);
+        const {uas, uac} = await this.srf.createB2BUA(this.req, this.res, uri, {
+          proxy,
+          headers,
+          responseHeaders,
+          proxyRequestHeaders: [
+            'all',
+            '-Authorization',
+            '-Max-Forwards',
+            '-Record-Route',
+            '-Session-Expires',
+            '-X-Subspace-Forwarded-For'
+          ],
+          proxyResponseHeaders: ['all', '-X-Trace-ID'],
+          localSdpB: spdOfferB,
+          localSdpA: async(sdp, res) => {
+            this.rtpEngineOpts.uac.tag = res.getParsedHeader('To').params.tag;
+            const opts = {
+              ...this.rtpEngineOpts.common,
+              ...this.rtpEngineOpts.uas.mediaOpts,
+              'from-tag': this.rtpEngineOpts.uas.tag,
+              'to-tag': this.rtpEngineOpts.uac.tag,
+              sdp
+            };
+            const startAt = process.hrtime();
+            const response = await this.answer(opts);
+            const rtt = roundTripTime(startAt);
+            this.stats.histogram('app.rtpengine.response_time', rtt, [
+              'direction:inbound', 'command:answer', `rtpengine:${this.rtpengineIp}`]);
+            if ('ok' !== response.result) {
+              this.logger.error(`rtpengine answer failed with ${JSON.stringify(response)}`);
+              throw new Error('rtpengine failed: answer');
+            }
+            return response.sdp;
+          }
+        });
+
+        // successfully connected
+        this.logger.info('call connected successfully to feature server');
+        debug('call connected successfully to feature server');
+        this._setHandlers({uas, uac});
+
+
+      } catch (err) {
+        // eslint-disable-next-line promise/no-promise-in-callback
+        this.rtpEngineResource.destroy()
+          .catch((err) => this.logger.info({err}, 'Error destroying rtpe after failure'));
+        this.activeCallIds.delete(this.req.get('Call-ID'));
+        this.stats.gauge('sbc.sip.calls.count', this.activeCallIds.size);
+        if (err instanceof SipError) {
+          const tags = ['accepted:no', `sipStatus:${err.status}`, `originator:${this.req.locals.originator}`];
+          this.stats.increment('sbc.terminations', tags);
+          this.logger.info(`call failed to connect to feature server with ${err.status}`);
+          this.emit('failed');
+        }
+        else if (err.message !== 'call canceled') {
+          this.logger.error(err, 'unexpected error routing inbound call');
+        }
+        this.srf.endSession(this.req);
       }
-      else if (err.message !== 'call canceled') {
-        this.logger.error(err, 'unexpected error routing inbound call');
-      }
-      this.srf.endSession(this.req);
-    }
+    });
   }
 
   _setDlgHandlers(dlg) {