diff --git a/Signal/src/UserInterface/Strings.swift b/Signal/src/UserInterface/Strings.swift
index b457b18ba..358a9314c 100644
--- a/Signal/src/UserInterface/Strings.swift
+++ b/Signal/src/UserInterface/Strings.swift
@@ -29,3 +29,8 @@ import Foundation
     static let missedCallWithIdentityChangeNotificationBodyWithoutCallerName =  NSLocalizedString("MISSED_CALL_WITH_CHANGED_IDENTITY_BODY_WITHOUT_CALLER_NAME", comment: "notification title")
     static let missedCallWithIdentityChangeNotificationBodyWithCallerName =  NSLocalizedString("MISSED_CALL_WITH_CHANGED_IDENTITY_BODY_WITH_CALLER_NAME", comment: "notification title. Embeds {{caller's name or phone number}}")
 }
+
+@objc class SafetyNumberStrings: NSObject {
+    static let confirmSendButton = NSLocalizedString("SAFETY_NUMBER_CHANGED_CONFIRM_SEND_ACTION",
+                                                      comment: "button title to confirm sending to a recipient whose safety number recently changed")
+}
diff --git a/Signal/src/ViewControllers/ConversationView/MessagesViewController.m b/Signal/src/ViewControllers/ConversationView/MessagesViewController.m
index ce78559e0..b744b7528 100644
--- a/Signal/src/ViewControllers/ConversationView/MessagesViewController.m
+++ b/Signal/src/ViewControllers/ConversationView/MessagesViewController.m
@@ -1167,8 +1167,7 @@ typedef enum : NSUInteger {
  *          NO if there were no unconfirmed identities
  */
 - (BOOL)showSafetyNumberConfirmationIfNecessaryWithConfirmationText:(NSString *)confirmationText
-                                                         completion:
-                                                             (void (^)(BOOL didConfirmedIdentity))completionHandler
+                                                         completion:(void (^)(BOOL didConfirmIdentity))completionHandler
 {
     return [SafetyNumberConfirmationAlert presentAlertIfNecessaryWithRecipientIds:self.thread.recipientIdentifiers
                                                                  confirmationText:confirmationText
@@ -1283,10 +1282,7 @@ typedef enum : NSUInteger {
     }
 
     BOOL didShowSNAlert =
-        [self showSafetyNumberConfirmationIfNecessaryWithConfirmationText:
-                  NSLocalizedString(@"SAFETY_NUMBER_CHANGED_CONFIRM_SEND_ACTION",
-                      @"button title to confirm sending to a recipient whose "
-                      @"safety number recently changed")
+        [self showSafetyNumberConfirmationIfNecessaryWithConfirmationText:[SafetyNumberStrings confirmSendButton]
                                                                completion:^(BOOL didConfirmIdentity) {
                                                                    if (didConfirmIdentity) {
                                                                        [weakSelf didPressSendButton:button
@@ -3704,10 +3700,7 @@ typedef enum : NSUInteger {
         }
 
         BOOL didShowSNAlert = [self
-            showSafetyNumberConfirmationIfNecessaryWithConfirmationText:
-                NSLocalizedString(@"SAFETY_NUMBER_CHANGED_CONFIRM_SEND_ACTION",
-                    @"button title to confirm sending to a recipient whose "
-                    @"safety number recently changed")
+            showSafetyNumberConfirmationIfNecessaryWithConfirmationText:[SafetyNumberStrings confirmSendButton]
                                                              completion:^(BOOL didConfirmIdentity) {
                                                                  if (didConfirmIdentity) {
                                                                      [weakSelf
diff --git a/Signal/src/ViewControllers/SendExternalFileViewController.m b/Signal/src/ViewControllers/SendExternalFileViewController.m
index d075d89cf..a1bf00c47 100644
--- a/Signal/src/ViewControllers/SendExternalFileViewController.m
+++ b/Signal/src/ViewControllers/SendExternalFileViewController.m
@@ -15,6 +15,7 @@ NS_ASSUME_NONNULL_BEGIN
 
 @interface SendExternalFileViewController () <SelectThreadViewControllerDelegate>
 
+@property (nonatomic, readonly) OWSContactsManager *contactsManager;
 @property (nonatomic, readonly) OWSMessageSender *messageSender;
 
 @end
@@ -35,6 +36,7 @@ NS_ASSUME_NONNULL_BEGIN
 {
     [super loadView];
 
+    _contactsManager = [Environment getCurrent].contactsManager;
     _messageSender = [Environment getCurrent].messageSender;
 
     self.title = NSLocalizedString(@"SEND_EXTERNAL_FILE_VIEW_TITLE", @"Title for the 'send external file' view.");
@@ -47,6 +49,21 @@ NS_ASSUME_NONNULL_BEGIN
     OWSAssert(self.attachment);
     OWSAssert(thread);
 
+    __weak typeof(self) weakSelf = self;
+
+    BOOL didShowSNAlert =
+        [SafetyNumberConfirmationAlert presentAlertIfNecessaryWithRecipientIds:thread.recipientIdentifiers
+                                                              confirmationText:[SafetyNumberStrings confirmSendButton]
+                                                               contactsManager:self.contactsManager
+                                                                    completion:^(BOOL didConfirm) {
+                                                                        if (didConfirm) {
+                                                                            [weakSelf threadWasSelected:thread];
+                                                                        }
+                                                                    }];
+    if (didShowSNAlert) {
+        return;
+    }
+
     [ThreadUtil sendMessageWithAttachment:self.attachment inThread:thread messageSender:self.messageSender];
 
     [Environment messageThreadId:thread.uniqueId];