diff --git a/src/Contacts/SignalRecipient.h b/src/Contacts/SignalRecipient.h
index 9509fbb88..7741808b6 100644
--- a/src/Contacts/SignalRecipient.h
+++ b/src/Contacts/SignalRecipient.h
@@ -1,17 +1,14 @@
-//
-//  TSRecipient.h
-//  TextSecureKit
-//
 //  Created by Frederic Jacobs on 17/11/14.
 //  Copyright (c) 2014 Open Whisper Systems. All rights reserved.
-//
 
 #import "TSYapDatabaseObject.h"
 
+NS_ASSUME_NONNULL_BEGIN
+
 @interface SignalRecipient : TSYapDatabaseObject
 
 - (instancetype)initWithTextSecureIdentifier:(NSString *)textSecureIdentifier
-                                       relay:(NSString *)relay
+                                       relay:(nullable NSString *)relay
                                supportsVoice:(BOOL)voiceCapable;
 
 + (instancetype)recipientWithTextSecureIdentifier:(NSString *)textSecureIdentifier
@@ -21,8 +18,10 @@
 
 - (void)removeDevices:(NSSet *)set;
 
-@property (nonatomic) NSString *relay;
+@property (nonatomic, nullable) NSString *relay;
 @property (nonatomic, retain) NSMutableOrderedSet *devices;
 @property BOOL supportsVoice;
 
 @end
+
+NS_ASSUME_NONNULL_END
diff --git a/src/Contacts/SignalRecipient.m b/src/Contacts/SignalRecipient.m
index 0a7a7f349..4cf2b28d1 100644
--- a/src/Contacts/SignalRecipient.m
+++ b/src/Contacts/SignalRecipient.m
@@ -1,14 +1,11 @@
-//
-//  TSRecipient.m
-//  TextSecureKit
-//
 //  Created by Frederic Jacobs on 17/11/14.
 //  Copyright (c) 2014 Open Whisper Systems. All rights reserved.
-//
 
 #import "SignalRecipient.h"
 #import "TSStorageManager+IdentityKeyStore.h"
 
+NS_ASSUME_NONNULL_BEGIN
+
 @implementation SignalRecipient
 
 + (NSString *)collection {
@@ -16,16 +13,18 @@
 }
 
 - (instancetype)initWithTextSecureIdentifier:(NSString *)textSecureIdentifier
-                                       relay:(NSString *)relay
-                               supportsVoice:(BOOL)voiceCapable {
+                                       relay:(nullable NSString *)relay
+                               supportsVoice:(BOOL)voiceCapable
+{
     self = [super initWithUniqueId:textSecureIdentifier];
-
-    if (self) {
-        _devices       = [NSMutableOrderedSet orderedSetWithObject:[NSNumber numberWithInt:1]];
-        _relay         = relay;
-        _supportsVoice = voiceCapable;
+    if (!self) {
+        return self;
     }
 
+    _devices = [NSMutableOrderedSet orderedSetWithObject:[NSNumber numberWithInt:1]];
+    _relay = [relay isEqualToString:@""] ? nil : relay;
+    _supportsVoice = voiceCapable;
+
     return self;
 }
 
@@ -55,3 +54,5 @@
 }
 
 @end
+
+NS_ASSUME_NONNULL_END
diff --git a/src/Contacts/Threads/TSContactThread.h b/src/Contacts/Threads/TSContactThread.h
index bb78c08c9..51c310136 100644
--- a/src/Contacts/Threads/TSContactThread.h
+++ b/src/Contacts/Threads/TSContactThread.h
@@ -1,17 +1,9 @@
-//
-//  TSContactThread.h
-//  TextSecureKit
-//
 //  Created by Frederic Jacobs on 16/11/14.
 //  Copyright (c) 2014 Open Whisper Systems. All rights reserved.
-//
 
-#import <Foundation/Foundation.h>
-
-#import "SignalRecipient.h"
 #import "TSThread.h"
 
-@class OWSSignalServiceProtosEnvelope;
+NS_ASSUME_NONNULL_BEGIN
 
 @interface TSContactThread : TSThread
 
@@ -20,8 +12,12 @@
 
 + (instancetype)getOrCreateThreadWithContactId:(NSString *)contactId
                                    transaction:(YapDatabaseReadWriteTransaction *)transaction
-                                      envelope:(OWSSignalServiceProtosEnvelope *)envelope;
+                                         relay:(nullable NSString *)relay;
+
+- (NSString *)contactIdentifier;
 
 - (NSString *)contactIdentifier;
 
 @end
+
+NS_ASSUME_NONNULL_END
diff --git a/src/Contacts/Threads/TSContactThread.m b/src/Contacts/Threads/TSContactThread.m
index 80c7ba2c9..261d13632 100644
--- a/src/Contacts/Threads/TSContactThread.m
+++ b/src/Contacts/Threads/TSContactThread.m
@@ -3,10 +3,11 @@
 
 #import "TSContactThread.h"
 #import "ContactsUpdater.h"
-#import "OWSSignalServiceProtos.pb.h"
 #import "TextSecureKitEnv.h"
 #import <YapDatabase/YapDatabaseTransaction.h>
 
+NS_ASSUME_NONNULL_BEGIN
+
 #define TSContactThreadPrefix @"c"
 
 @implementation TSContactThread
@@ -21,13 +22,12 @@
 
 + (instancetype)getOrCreateThreadWithContactId:(NSString *)contactId
                                    transaction:(YapDatabaseReadWriteTransaction *)transaction
-                                      envelope:(OWSSignalServiceProtosEnvelope *)envelope
+                                         relay:(nullable NSString *)relay
 {
     SignalRecipient *recipient =
         [SignalRecipient recipientWithTextSecureIdentifier:contactId withTransaction:transaction];
 
     if (!recipient) {
-        NSString *relay = envelope.hasRelay && ![envelope.relay isEqualToString:@""] ? envelope.relay : nil;
         recipient = [[SignalRecipient alloc] initWithTextSecureIdentifier:contactId relay:relay supportsVoice:YES];
 
         [[ContactsUpdater sharedUpdater] lookupIdentifier:contactId
@@ -76,7 +76,8 @@
 
 #if TARGET_OS_IPHONE
 
-- (UIImage *)image {
+- (nullable UIImage *)image
+{
     UIImage *image = [[TextSecureKitEnv sharedEnv].contactsManager imageForPhoneIdentifier:self.contactIdentifier];
     return image;
 }
@@ -92,3 +93,5 @@
 }
 
 @end
+
+NS_ASSUME_NONNULL_END
diff --git a/src/Messages/InvalidKeyMessages/TSInvalidIdentityKeySendingErrorMessage.m b/src/Messages/InvalidKeyMessages/TSInvalidIdentityKeySendingErrorMessage.m
index 24a8fd63c..2cba98885 100644
--- a/src/Messages/InvalidKeyMessages/TSInvalidIdentityKeySendingErrorMessage.m
+++ b/src/Messages/InvalidKeyMessages/TSInvalidIdentityKeySendingErrorMessage.m
@@ -1,22 +1,16 @@
-//
-//  TSInvalidIdentityKeySendingErrorMessage.m
-//  Signal
-//
 //  Created by Frederic Jacobs on 15/02/15.
 //  Copyright (c) 2015 Open Whisper Systems. All rights reserved.
-//
-
-#import "TSOutgoingMessage.h"
-
-#import <AxolotlKit/NSData+keyVersionByte.h>
 
+#import "TSInvalidIdentityKeySendingErrorMessage.h"
 #import "PreKeyBundle+jsonDict.h"
+#import "SignalRecipient.h"
 #import "TSContactThread.h"
 #import "TSErrorMessage_privateConstructor.h"
 #import "TSFingerprintGenerator.h"
-#import "TSInvalidIdentityKeySendingErrorMessage.h"
 #import "TSMessagesManager+sendMessages.h"
+#import "TSOutgoingMessage.h"
 #import "TSStorageManager+IdentityKeyStore.h"
+#import <AxolotlKit/NSData+keyVersionByte.h>
 
 @interface TSInvalidIdentityKeySendingErrorMessage ()
 
diff --git a/src/Messages/TSMessagesManager.m b/src/Messages/TSMessagesManager.m
index 0b4a2394e..63ffbf5aa 100644
--- a/src/Messages/TSMessagesManager.m
+++ b/src/Messages/TSMessagesManager.m
@@ -341,7 +341,7 @@
       } else {
           TSContactThread *cThread = [TSContactThread getOrCreateThreadWithContactId:envelope.source
                                                                          transaction:transaction
-                                                                            envelope:envelope];
+                                                                               relay:envelope.relay];
 
           incomingMessage = [[TSIncomingMessage alloc] initWithTimestamp:timeStamp
                                                                 inThread:cThread