diff --git a/lib/call-session.js b/lib/call-session.js
index c968152..1ec3530 100644
--- a/lib/call-session.js
+++ b/lib/call-session.js
@@ -80,6 +80,10 @@ class CallSession extends Emitter {
     return tp && -1 !== tp.indexOf('SAVP');
   }
 
+  get isFive9VoiceStream() {
+    return this.req.has('X-Five9-StreamingPairId');
+  }
+
   async connect() {
     const {sdp} = this.req.locals;
     this.logger.info('inbound call accepted for routing');
@@ -168,6 +172,13 @@ class CallSession extends Emitter {
         throw new Error('rtpengine failed: answer');
       }
 
+      /* special case: Five9 Voicestream calls do not advertise a:sendonly, though they should */
+      if (this.isFive9VoiceStream) {
+        this.logger.info('Voicestream call from Five9, blocking audio in the reverse direction');
+        const response = Promise.all([this.blockMedia(opts), this.blockDTMF(opts)]);
+        this.logger.debug({response}, 'response to blocMedia');
+      }
+
       let headers = {
         'From': createBLegFromHeader(this.req),
         'To': this.req.get('To'),