diff --git a/includes/functions/comments/_comments_threads.php b/includes/functions/comments/_comments_threads.php
index 3b604d62..45417fc8 100644
--- a/includes/functions/comments/_comments_threads.php
+++ b/includes/functions/comments/_comments_threads.php
@@ -756,7 +756,7 @@ if ( ! function_exists( 'fictioneer_theme_comment' ) ) {
               data-dialog-message="<?php echo esc_attr(
                 sprintf(
                   __( 'Are you sure you want to delete your comment? Enter %s to confirm.', 'fictioneer' ),
-                  strtoupper( _x( 'delete', 'Prompt confirm deletion string.', 'fictioneer' ) )
+                  mb_strtoupper( _x( 'delete', 'Prompt confirm deletion string.', 'fictioneer' ) )
                 )
               ); ?>"
               data-dialog-confirm="<?php echo esc_attr_x( 'delete', 'Prompt confirm deletion string.', 'fictioneer' ); ?>"
diff --git a/includes/functions/settings/_settings_page_setup.php b/includes/functions/settings/_settings_page_setup.php
index 75b0a4d4..aee48bc0 100644
--- a/includes/functions/settings/_settings_page_setup.php
+++ b/includes/functions/settings/_settings_page_setup.php
@@ -8,8 +8,6 @@
  */
 
 
-// Setup
-
 ?>
 
 <div class="fictioneer-settings">
diff --git a/includes/functions/users/_admin-profile.php b/includes/functions/users/_admin-profile.php
index 5ff55111..c924056e 100644
--- a/includes/functions/users/_admin-profile.php
+++ b/includes/functions/users/_admin-profile.php
@@ -1124,7 +1124,7 @@ function fictioneer_admin_profile_fields_oauth( $profile_user ) {
           $id_hash = get_the_author_meta( "fictioneer_{$provider[0]}_id_hash", $profile_user->ID ) ?: null;
           $confirmation_message = sprintf(
             __( 'Are you sure? Note that if you disconnect all accounts, you may no longer be able to log back in once you log out. Enter %s to confirm.', 'fictioneer' ),
-            strtoupper( $confirmation_string )
+            mb_strtoupper( $confirmation_string )
           );
 
           if ( $client_id && $client_secret ) {
@@ -1305,7 +1305,7 @@ function fictioneer_admin_profile_fields_data_nodes( $profile_user ) {
             $confirmation_message = sprintf(
               __( 'Are you sure you want to clear your %s? This action is irreversible. Enter %s to confirm.', 'fictioneer' ),
               str_replace( '-', ' ', $node[0] ),
-              strtoupper( $confirmation_string )
+              mb_strtoupper( $confirmation_string )
             );
           ?>
           <div class="data-node">
@@ -2073,7 +2073,7 @@ function fictioneer_admin_danger_zone( $profile_user ) {
   $confirmation_string = _x( 'delete', 'Prompt confirm deletion string.', 'fictioneer' );
   $confirmation_message = sprintf(
     __( 'Are you sure? Your account will be irrevocably deleted, although this will not remove your comments. Enter %s to confirm.', 'fictioneer' ),
-    strtoupper( $confirmation_string )
+    mb_strtoupper( $confirmation_string )
   );
 
   $deletion_url = add_query_arg(
diff --git a/singular-index-advanced.php b/singular-index-advanced.php
index ee52130a..4b819ca8 100644
--- a/singular-index-advanced.php
+++ b/singular-index-advanced.php
@@ -102,7 +102,7 @@ reset( $sorted_stories );
 
         <section class="index-letters">
           <?php foreach ( $sorted_stories as $index => $stories ) : ?>
-            <a href="<?php echo esc_attr( "#letter-{$index}" ); ?>" class="index-letters__letter"><?php echo strtoupper( $index ); ?></a>
+            <a href="<?php echo esc_attr( "#letter-{$index}" ); ?>" class="index-letters__letter"><?php echo mb_strtoupper( $index ); ?></a>
             <?php if ( $last_key !== $index ) : ?>
               <span class="index-letters__separator">&bull;</span>
             <?php endif; ?>
@@ -112,7 +112,7 @@ reset( $sorted_stories );
         <?php foreach ( $sorted_stories as $index => $stories ) : ?>
           <section class="glossary">
 
-            <h2 id="<?php echo esc_attr( "letter-{$index}" ); ?>"><?php echo strtoupper( $index ); ?></h2>
+            <h2 id="<?php echo esc_attr( "letter-{$index}" ); ?>"><?php echo mb_strtoupper( $index ); ?></h2>
 
             <div class="glossary__columns">
 
diff --git a/singular-index.php b/singular-index.php
index 1669a916..f88557aa 100644
--- a/singular-index.php
+++ b/singular-index.php
@@ -98,7 +98,7 @@ reset( $sorted_stories );
 
         <section class="index-letters">
           <?php foreach ( $sorted_stories as $index => $stories ) : ?>
-            <a href="<?php echo esc_attr( "#letter-{$index}" ); ?>" class="index-letters__letter"><?php echo strtoupper( $index ); ?></a>
+            <a href="<?php echo esc_attr( "#letter-{$index}" ); ?>" class="index-letters__letter"><?php echo mb_strtoupper( $index ); ?></a>
             <?php if ( $last_key !== $index ) : ?>
               <span class="index-letters__separator">&bull;</span>
             <?php endif; ?>
@@ -108,7 +108,7 @@ reset( $sorted_stories );
         <?php foreach ( $sorted_stories as $index => $stories ) : ?>
           <section class="glossary">
 
-            <h2 id="<?php echo esc_attr( "letter-{$index}" ); ?>"><?php echo strtoupper( $index ); ?></h2>
+            <h2 id="<?php echo esc_attr( "letter-{$index}" ); ?>"><?php echo mb_strtoupper( $index ); ?></h2>
 
             <div class="glossary__columns">