diff --git a/Signal/src/ViewControllers/ConversationView/Cells/AttachmentUploadView.m b/Signal/src/ViewControllers/ConversationView/Cells/AttachmentUploadView.m
index bb6785950..cf28de377 100644
--- a/Signal/src/ViewControllers/ConversationView/Cells/AttachmentUploadView.m
+++ b/Signal/src/ViewControllers/ConversationView/Cells/AttachmentUploadView.m
@@ -80,7 +80,7 @@ NS_ASSUME_NONNULL_BEGIN
     self.progressLabel = [UILabel new];
     self.progressLabel.text = NSLocalizedString(
         @"MESSAGE_METADATA_VIEW_MESSAGE_STATUS_UPLOADING", @"Status label for messages which are uploading.")
-                                  .uppercaseString;
+                                  .localizedUppercaseString;
     self.progressLabel.textColor = UIColor.whiteColor;
     self.progressLabel.font = [UIFont ows_dynamicTypeCaption1Font];
     self.progressLabel.textAlignment = NSTextAlignmentCenter;
diff --git a/Signal/src/ViewControllers/ConversationView/Cells/OWSAudioMessageView.m b/Signal/src/ViewControllers/ConversationView/Cells/OWSAudioMessageView.m
index 029cdb0a4..e167b21c5 100644
--- a/Signal/src/ViewControllers/ConversationView/Cells/OWSAudioMessageView.m
+++ b/Signal/src/ViewControllers/ConversationView/Cells/OWSAudioMessageView.m
@@ -194,7 +194,7 @@ NS_ASSUME_NONNULL_BEGIN
     }
     NSString *topText = [[filename stringByDeletingPathExtension] ows_stripped];
     if (topText.length < 1) {
-        topText = [MIMETypeUtil fileExtensionForMIMEType:self.attachmentStream.contentType].uppercaseString;
+        topText = [MIMETypeUtil fileExtensionForMIMEType:self.attachmentStream.contentType].localizedUppercaseString;
     }
     if (topText.length < 1) {
         topText = NSLocalizedString(@"GENERIC_ATTACHMENT_LABEL", @"A label for generic attachments.");
diff --git a/Signal/src/ViewControllers/ConversationView/Cells/OWSGenericAttachmentView.m b/Signal/src/ViewControllers/ConversationView/Cells/OWSGenericAttachmentView.m
index 78907a2ca..a43991249 100644
--- a/Signal/src/ViewControllers/ConversationView/Cells/OWSGenericAttachmentView.m
+++ b/Signal/src/ViewControllers/ConversationView/Cells/OWSGenericAttachmentView.m
@@ -113,7 +113,7 @@ NS_ASSUME_NONNULL_BEGIN
     }
 
     UILabel *fileTypeLabel = [UILabel new];
-    fileTypeLabel.text = fileExtension.uppercaseString;
+    fileTypeLabel.text = fileExtension.localizedUppercaseString;
     fileTypeLabel.textColor = [UIColor ows_light90Color];
     fileTypeLabel.lineBreakMode = NSLineBreakByTruncatingTail;
     fileTypeLabel.font = [UIFont ows_dynamicTypeCaption1Font].ows_mediumWeight;
@@ -132,7 +132,7 @@ NS_ASSUME_NONNULL_BEGIN
 
     NSString *topText = [self.attachmentStream.sourceFilename ows_stripped];
     if (topText.length < 1) {
-        topText = [MIMETypeUtil fileExtensionForMIMEType:self.attachmentStream.contentType].uppercaseString;
+        topText = [MIMETypeUtil fileExtensionForMIMEType:self.attachmentStream.contentType].localizedUppercaseString;
     }
     if (topText.length < 1) {
         topText = NSLocalizedString(@"GENERIC_ATTACHMENT_LABEL", @"A label for generic attachments.");
diff --git a/Signal/src/ViewControllers/ConversationView/Cells/OWSMessageCell.m b/Signal/src/ViewControllers/ConversationView/Cells/OWSMessageCell.m
index 6aa0fe4f7..515a3142c 100644
--- a/Signal/src/ViewControllers/ConversationView/Cells/OWSMessageCell.m
+++ b/Signal/src/ViewControllers/ConversationView/Cells/OWSMessageCell.m
@@ -276,7 +276,7 @@ NS_ASSUME_NONNULL_BEGIN
         NSString *timeString = [dateHeaderTimeFormatter stringFromDate:date];
 
         NSAttributedString *attributedText = [NSAttributedString new];
-        attributedText = [attributedText rtlSafeAppend:dateString.uppercaseString
+        attributedText = [attributedText rtlSafeAppend:dateString.localizedUppercaseString
                                             attributes:@{
                                                 NSFontAttributeName : self.dateHeaderFont,
                                                 NSForegroundColorAttributeName : [UIColor lightGrayColor],
diff --git a/Signal/src/ViewControllers/ConversationView/Cells/OWSUnreadIndicatorCell.m b/Signal/src/ViewControllers/ConversationView/Cells/OWSUnreadIndicatorCell.m
index 5bd612c45..9b9c9c066 100644
--- a/Signal/src/ViewControllers/ConversationView/Cells/OWSUnreadIndicatorCell.m
+++ b/Signal/src/ViewControllers/ConversationView/Cells/OWSUnreadIndicatorCell.m
@@ -115,7 +115,7 @@ NS_ASSUME_NONNULL_BEGIN
 - (NSString *)titleForInteraction:(TSUnreadIndicatorInteraction *)interaction
 {
     return NSLocalizedString(@"MESSAGES_VIEW_UNREAD_INDICATOR", @"Indicator that separates read from unread messages.")
-        .uppercaseString;
+        .localizedUppercaseString;
 }
 
 - (NSString *)subtitleForInteraction:(TSUnreadIndicatorInteraction *)interaction
diff --git a/Signal/src/ViewControllers/Registration/RegistrationViewController.m b/Signal/src/ViewControllers/Registration/RegistrationViewController.m
index dd957f5d7..2cc779ca5 100644
--- a/Signal/src/ViewControllers/Registration/RegistrationViewController.m
+++ b/Signal/src/ViewControllers/Registration/RegistrationViewController.m
@@ -373,7 +373,7 @@ NSString *const kKeychainKey_LastRegisteredPhoneNumber = @"kKeychainKey_LastRegi
     _countryCode = countryCode;
     _callingCode = callingCode;
 
-    NSString *title = [NSString stringWithFormat:@"%@ (%@)", callingCode, countryCode.uppercaseString];
+    NSString *title = [NSString stringWithFormat:@"%@ (%@)", callingCode, countryCode.localizedUppercaseString];
     self.countryCodeLabel.text = title;
     [self.countryCodeLabel setNeedsLayout];
 
diff --git a/Signal/src/util/DateUtil.m b/Signal/src/util/DateUtil.m
index 38e1bb47e..28aece134 100644
--- a/Signal/src/util/DateUtil.m
+++ b/Signal/src/util/DateUtil.m
@@ -203,7 +203,7 @@ static NSString *const DATE_FORMAT_WEEKDAY = @"EEEE";
         dateTimeString = [[DateUtil timeFormatter] stringFromDate:date];
     }
 
-    return dateTimeString.uppercaseString;
+    return dateTimeString.localizedUppercaseString;
 }
 
 + (NSString *)formatTimestampAsTime:(uint64_t)timestamp
@@ -216,7 +216,7 @@ static NSString *const DATE_FORMAT_WEEKDAY = @"EEEE";
     OWSAssert(date);
 
     NSString *dateTimeString = [[DateUtil timeFormatter] stringFromDate:date];
-    return dateTimeString.uppercaseString;
+    return dateTimeString.localizedUppercaseString;
 }
 
 + (NSDateFormatter *)otherYearMessageFormatter
@@ -320,7 +320,7 @@ static NSString *const DATE_FORMAT_WEEKDAY = @"EEEE";
 
 + (NSString *)exemplaryNowTimeFormat
 {
-    return NSLocalizedString(@"DATE_NOW", @"The present; the current time.").uppercaseString;
+    return NSLocalizedString(@"DATE_NOW", @"The present; the current time.").localizedUppercaseString;
 }
 
 + (NSString *)exemplaryMinutesTimeFormat
diff --git a/SignalMessaging/contacts/SelectRecipientViewController.m b/SignalMessaging/contacts/SelectRecipientViewController.m
index bcb494a70..506f8e44e 100644
--- a/SignalMessaging/contacts/SelectRecipientViewController.m
+++ b/SignalMessaging/contacts/SelectRecipientViewController.m
@@ -243,7 +243,7 @@ NSString *const kSelectRecipientViewControllerCellIdentifier = @"kSelectRecipien
     _callingCode = callingCode;
 
     NSString *titleFormat = (CurrentAppContext().isRTL ? @"(%2$@) %1$@" : @"%1$@ (%2$@)");
-    NSString *title = [NSString stringWithFormat:titleFormat, callingCode, countryCode.uppercaseString];
+    NSString *title = [NSString stringWithFormat:titleFormat, callingCode, countryCode.localizedUppercaseString];
     [self.countryCodeButton setTitle:title forState:UIControlStateNormal];
     [self.countryCodeButton layoutSubviews];
 
diff --git a/SignalMessaging/utils/OWSContactAvatarBuilder.m b/SignalMessaging/utils/OWSContactAvatarBuilder.m
index add15038f..c190f5145 100644
--- a/SignalMessaging/utils/OWSContactAvatarBuilder.m
+++ b/SignalMessaging/utils/OWSContactAvatarBuilder.m
@@ -111,7 +111,7 @@ NS_ASSUME_NONNULL_BEGIN
             NSString *trimmedWord = [word stringByTrimmingCharactersInSet:excludeAlphanumeric];
             if (trimmedWord.length > 0) {
                 NSString *firstLetter = [trimmedWord substringToIndex:1];
-                [initials appendString:[firstLetter uppercaseString]];
+                [initials appendString:firstLetter.localizedUppercaseString];
             }
         }