diff --git a/Signal/src/call/CallService.swift b/Signal/src/call/CallService.swift
index fbdf5e9d0..1763380b2 100644
--- a/Signal/src/call/CallService.swift
+++ b/Signal/src/call/CallService.swift
@@ -399,7 +399,7 @@ protocol CallServiceObserver: class {
         }
 
         guard call.signalingId == callId else {
-            Logger.warn("\(self.TAG) ignoring obsolete call: \(callId) in \(#function)")
+            Logger.warn("\(self.TAG) ignoring mismatched call: \(callId) currentCall: \(call.signalingId) in \(#function)")
             return
         }
 
@@ -480,12 +480,17 @@ protocol CallServiceObserver: class {
     /**
      * The callee was already in another call.
      */
-    public func handleRemoteBusy(thread: TSContactThread) {
+    public func handleRemoteBusy(thread: TSContactThread, callId: UInt64) {
         Logger.info("\(TAG) \(#function) for thread: \(thread.contactIdentifier())")
         AssertIsOnMainThread()
 
         guard let call = self.call else {
-            Logger.warn("\(self.TAG) ignoring obsolete call in \(#function)")
+            Logger.warn("\(self.TAG) ignoring obsolete call: \(callId) in \(#function)")
+            return
+        }
+
+        guard call.signalingId == callId else {
+            Logger.warn("\(self.TAG) ignoring mismatched call: \(callId) currentCall: \(call.signalingId) in \(#function)")
             return
         }
 
@@ -541,13 +546,15 @@ protocol CallServiceObserver: class {
         }
 
         guard self.call == nil else {
+            let existingCall = self.call!
+
             // TODO on iOS10+ we can use CallKit to swap calls rather than just returning busy immediately.
-            Logger.info("\(TAG) receivedCallOffer: \(newCall.identifiersForLogs) but we're already in call: \(call!.identifiersForLogs)")
+            Logger.info("\(TAG) receivedCallOffer: \(newCall.identifiersForLogs) but we're already in call: \(existingCall.identifiersForLogs)")
 
             handleLocalBusyCall(newCall, thread: thread)
 
-            if self.call!.remotePhoneNumber == newCall.remotePhoneNumber {
-                Logger.info("\(TAG) handling call from current call user as remote busy.: \(newCall.identifiersForLogs) but we're already in call: \(call!.identifiersForLogs)")
+            if existingCall.remotePhoneNumber == newCall.remotePhoneNumber {
+                Logger.info("\(TAG) handling call from current call user as remote busy.: \(newCall.identifiersForLogs) but we're already in call: \(existingCall.identifiersForLogs)")
 
                 // If we're receiving a new call offer from the user we already think we have a call with,
                 // terminate our current call to get back to a known good state.  If they call back, we'll 
@@ -556,11 +563,11 @@ protocol CallServiceObserver: class {
                 // TODO: Auto-accept this incoming call if our current call was either a) outgoing or 
                 // b) never connected.  There will be a bit of complexity around making sure that two
                 // parties that call each other at the same time end up connected.
-                switch self.call!.state {
+                switch existingCall.state {
                 case .idle, .dialing, .remoteRinging:
                     // If both users are trying to call each other at the same time,
                     // both should see busy.
-                    handleRemoteBusy(thread:self.call!.thread)
+                    handleRemoteBusy(thread:existingCall.thread, callId:existingCall.signalingId)
                 case .answering, .localRinging, .connected, .localFailure, .localHangup, .remoteHangup, .remoteBusy:
                     // If one user calls another while the other has a "vestigial" call with
                     // that same user, fail the old call.
@@ -683,7 +690,7 @@ protocol CallServiceObserver: class {
             }
 
             guard call.signalingId == callId else {
-                Logger.warn("ignoring remote ice update for thread: \(thread.uniqueId) due to callId mismatch. Call already ended?")
+                Logger.warn("\(self.TAG) ignoring mismatched call: \(callId) currentCall: \(call.signalingId) in \(#function)")
                 return
             }
 
@@ -791,7 +798,7 @@ protocol CallServiceObserver: class {
     /**
      * The remote client (caller or callee) ended the call.
      */
-    public func handleRemoteHangup(thread: TSContactThread) {
+    public func handleRemoteHangup(thread: TSContactThread, callId: UInt64) {
         Logger.debug("\(TAG) in \(#function)")
         AssertIsOnMainThread()
 
@@ -801,6 +808,11 @@ protocol CallServiceObserver: class {
             return
         }
 
+        guard call.signalingId == callId else {
+            Logger.warn("\(self.TAG) ignoring mismatched call: \(callId) currentCall: \(call.signalingId) in \(#function)")
+            return
+        }
+
         guard thread.contactIdentifier() == call.thread.contactIdentifier() else {
             // This can safely be ignored.
             // We don't want to fail the current call because an old call was slow to send us the hangup message.
@@ -1161,7 +1173,7 @@ protocol CallServiceObserver: class {
                 return
             }
 
-            handleRemoteHangup(thread: call.thread)
+            handleRemoteHangup(thread: call.thread, callId: hangup.id)
         } else if message.hasVideoStreamingStatus() {
             Logger.debug("\(TAG) remote participant sent VideoStreamingStatus via data channel: \(call.identifiersForLogs).")
 
diff --git a/Signal/src/call/WebRTCCallMessageHandler.swift b/Signal/src/call/WebRTCCallMessageHandler.swift
index 80adc4b21..304c2a739 100644
--- a/Signal/src/call/WebRTCCallMessageHandler.swift
+++ b/Signal/src/call/WebRTCCallMessageHandler.swift
@@ -29,6 +29,10 @@ class WebRTCCallMessageHandler: NSObject, OWSCallMessageHandler {
 
     public func receivedOffer(_ offer: OWSSignalServiceProtosCallMessageOffer, from callerId: String) {
         AssertIsOnMainThread()
+        guard offer.hasId() else {
+            owsFail("no callId in \(#function)")
+            return
+        }
 
         let thread = TSContactThread.getOrCreateThread(contactId: callerId)
         self.callService.handleReceivedOffer(thread: thread, callId: offer.id, sessionDescription: offer.sessionDescription)
@@ -36,6 +40,10 @@ class WebRTCCallMessageHandler: NSObject, OWSCallMessageHandler {
 
     public func receivedAnswer(_ answer: OWSSignalServiceProtosCallMessageAnswer, from callerId: String) {
         AssertIsOnMainThread()
+        guard answer.hasId() else {
+            owsFail("no callId in \(#function)")
+            return
+        }
 
         let thread = TSContactThread.getOrCreateThread(contactId: callerId)
         self.callService.handleReceivedAnswer(thread: thread, callId: answer.id, sessionDescription: answer.sessionDescription)
@@ -43,6 +51,10 @@ class WebRTCCallMessageHandler: NSObject, OWSCallMessageHandler {
 
     public func receivedIceUpdate(_ iceUpdate: OWSSignalServiceProtosCallMessageIceUpdate, from callerId: String) {
         AssertIsOnMainThread()
+        guard iceUpdate.hasId() else {
+            owsFail("no callId in \(#function)")
+            return
+        }
 
         let thread = TSContactThread.getOrCreateThread(contactId: callerId)
 
@@ -55,18 +67,24 @@ class WebRTCCallMessageHandler: NSObject, OWSCallMessageHandler {
 
     public func receivedHangup(_ hangup: OWSSignalServiceProtosCallMessageHangup, from callerId: String) {
         AssertIsOnMainThread()
+        guard hangup.hasId() else {
+            owsFail("no callId in \(#function)")
+            return
+        }
 
         let thread = TSContactThread.getOrCreateThread(contactId: callerId)
-
-        self.callService.handleRemoteHangup(thread: thread)
+        self.callService.handleRemoteHangup(thread: thread, callId: hangup.id)
     }
 
     public func receivedBusy(_ busy: OWSSignalServiceProtosCallMessageBusy, from callerId: String) {
         AssertIsOnMainThread()
+        guard busy.hasId() else {
+            owsFail("no callId in \(#function)")
+            return
+        }
 
         let thread = TSContactThread.getOrCreateThread(contactId: callerId)
-
-        self.callService.handleRemoteBusy(thread: thread)
+        self.callService.handleRemoteBusy(thread: thread, callId: busy.id)
     }
 
 }