diff --git a/Signal/translations/en.lproj/Localizable.strings b/Signal/translations/en.lproj/Localizable.strings
index ed1421f23..a240fbf3a 100644
--- a/Signal/translations/en.lproj/Localizable.strings
+++ b/Signal/translations/en.lproj/Localizable.strings
@@ -857,7 +857,7 @@
 /* No comment provided by engineer. */
 "ERROR_MESSAGE_WRONG_TRUSTED_IDENTITY_KEY" = "Safety number changed. Tap to verify.";
 
-/* Format string for 'unregistered user' error. Embeds {{the unregistered user's signal id}}. */
+/* Format string for 'unregistered user' error. Embeds {{the unregistered user's name or signal id}}. */
 "ERROR_UNREGISTERED_USER_FORMAT" = "Unregistered User: %@";
 
 /* action sheet header when re-sending message which failed because of too many attempts */
diff --git a/SignalServiceKit/src/Messages/Interactions/TSInfoMessage.m b/SignalServiceKit/src/Messages/Interactions/TSInfoMessage.m
index 82c6c7b4e..b9a181158 100644
--- a/SignalServiceKit/src/Messages/Interactions/TSInfoMessage.m
+++ b/SignalServiceKit/src/Messages/Interactions/TSInfoMessage.m
@@ -3,7 +3,9 @@
 //
 
 #import "TSInfoMessage.h"
+#import "ContactsManagerProtocol.h"
 #import "NSDate+OWS.h"
+#import "TextSecureKitEnv.h"
 #import <YapDatabase/YapDatabaseConnection.h>
 
 NS_ASSUME_NONNULL_BEGIN
@@ -118,10 +120,12 @@ NSUInteger TSInfoMessageSchemaVersion = 1;
             return NSLocalizedString(@"UNSUPPORTED_ATTACHMENT", nil);
         case TSInfoMessageUserNotRegistered:
             if (self.unregisteredRecipientId.length > 0) {
+                id<ContactsManagerProtocol> contactsManager = [TextSecureKitEnv sharedEnv].contactsManager;
+                NSString *recipientName = [contactsManager displayNameForPhoneIdentifier:self.unregisteredRecipientId];
                 return [NSString stringWithFormat:NSLocalizedString(@"ERROR_UNREGISTERED_USER_FORMAT",
                                                       @"Format string for 'unregistered user' error. Embeds {{the "
-                                                      @"unregistered user's signal id}}."),
-                                 self.unregisteredRecipientId];
+                                                      @"unregistered user's name or signal id}}."),
+                                 recipientName];
             } else {
                 return NSLocalizedString(@"CONTACT_DETAIL_COMM_TYPE_INSECURE", nil);
             }
diff --git a/SignalServiceKit/src/Messages/OWSBlockingManager.h b/SignalServiceKit/src/Messages/OWSBlockingManager.h
index 25dd3d24f..56757f75e 100644
--- a/SignalServiceKit/src/Messages/OWSBlockingManager.h
+++ b/SignalServiceKit/src/Messages/OWSBlockingManager.h
@@ -29,5 +29,4 @@ extern NSString *const kNSNotificationName_BlockedPhoneNumbersDidChange;
 
 @end
 
-
 NS_ASSUME_NONNULL_END
diff --git a/SignalServiceKit/src/Protocols/ContactsManagerProtocol.h b/SignalServiceKit/src/Protocols/ContactsManagerProtocol.h
index 122ddaead..64d7e0335 100644
--- a/SignalServiceKit/src/Protocols/ContactsManagerProtocol.h
+++ b/SignalServiceKit/src/Protocols/ContactsManagerProtocol.h
@@ -2,6 +2,8 @@
 //  Copyright (c) 2018 Open Whisper Systems. All rights reserved.
 //
 
+NS_ASSUME_NONNULL_BEGIN
+
 @class Contact;
 @class PhoneNumber;
 @class SignalAccount;
@@ -9,10 +11,12 @@
 
 @protocol ContactsManagerProtocol <NSObject>
 
-- (NSString * _Nonnull)displayNameForPhoneIdentifier:(NSString * _Nullable)phoneNumber;
-- (NSArray<SignalAccount *> * _Nonnull)signalAccounts;
+- (NSString *)displayNameForPhoneIdentifier:(NSString *_Nullable)phoneNumber;
+- (NSArray<SignalAccount *> *)signalAccounts;
 
 - (BOOL)isSystemContact:(NSString *)recipientId;
 - (BOOL)isSystemContactWithSignalAccount:(NSString *)recipientId;
 
 @end
+
+NS_ASSUME_NONNULL_END