diff --git a/lib/session/call-session.js b/lib/session/call-session.js
index 6d45f4d3..f50ccb44 100644
--- a/lib/session/call-session.js
+++ b/lib/session/call-session.js
@@ -533,7 +533,10 @@ class CallSession extends Emitter {
   getMS() {
     if (!this.ms) {
       this.ms = this.srf.locals.getFreeswitch();
-      if (!this.ms) throw new Error('no available freeswitch');
+      if (!this.ms) {
+        this._mediaServerFailure = true;
+        throw new Error('no available freeswitch');
+      }
     }
     return this.ms;
   }
diff --git a/lib/session/inbound-call-session.js b/lib/session/inbound-call-session.js
index 70e74972..f591a53e 100644
--- a/lib/session/inbound-call-session.js
+++ b/lib/session/inbound-call-session.js
@@ -28,8 +28,18 @@ class InboundCallSession extends CallSession {
 
   _onTasksDone() {
     if (!this.res.finalResponseSent) {
-      this.logger.info('InboundCallSession:_onTasksDone auto-generating non-success response to invite');
-      this.res.send(603);
+      if (this._mediaServerFailure) {
+        this.logger.info('InboundCallSession:_onTasksDone generating 480 due to media server failure');
+        this.res.send(480, {
+          headers: {
+            'X-Reason': 'crankback: media server failure'
+          }
+        });
+      }
+      else {
+        this.logger.info('InboundCallSession:_onTasksDone auto-generating non-success response to invite');
+        this.res.send(603);
+      }
     }
   }