diff --git a/includes/functions/_module-epub.php b/includes/functions/_module-epub.php
index 4e13ebaf..276b200d 100644
--- a/includes/functions/_module-epub.php
+++ b/includes/functions/_module-epub.php
@@ -1134,7 +1134,7 @@ function fictioneer_generate_epub() {
   $mimetype_path = $uploads_dir . $folder . '/mimetype';
   $files = new RecursiveIteratorIterator( new RecursiveDirectoryIterator( $directory ), RecursiveIteratorIterator::LEAVES_ONLY );
 
-  $zip->addFile( $mimetype_path, substr( $mimetype_path, strlen( $directory ) + 1) );
+  $zip->addFile( $mimetype_path, substr( $mimetype_path, mb_strlen( $directory ) + 1) );
 
   foreach ( $files as $name => $file ) {
     if ( $name == 'mimetype' ) {
@@ -1143,7 +1143,7 @@ function fictioneer_generate_epub() {
 
     if ( ! $file->isDir() ) {
       $filePath = $file->getRealPath();
-      $relativePath = substr( $filePath, strlen( $directory ) + 1);
+      $relativePath = substr( $filePath, mb_strlen( $directory ) + 1);
 
       $zip->addFile( $filePath, $relativePath );
     }
diff --git a/partials/_card-recommendation.php b/partials/_card-recommendation.php
index 971a4754..f0892097 100644
--- a/partials/_card-recommendation.php
+++ b/partials/_card-recommendation.php
@@ -113,7 +113,7 @@ $thumbnail_args = array(
             _x( 'by %s —', 'Large card: by {Author} —.', 'fictioneer' ),
             get_post_meta( $post_id, 'fictioneer_recommendation_author', true )
           ),
-          strlen( $one_sentence ) < strlen( $excerpt ) ? $excerpt : wp_strip_all_tags( $one_sentence, true )
+          mb_strlen( $one_sentence ) < mb_strlen( $excerpt ) ? $excerpt : wp_strip_all_tags( $one_sentence, true )
         );
       ?>
 
diff --git a/partials/_latest-chapters.php b/partials/_latest-chapters.php
index 4604f13f..a29eac99 100644
--- a/partials/_latest-chapters.php
+++ b/partials/_latest-chapters.php
@@ -269,11 +269,11 @@ remove_filter( 'posts_where', 'fictioneer_exclude_protected_posts' );
 
                     $excerpt = fictioneer_get_forced_excerpt( $post );
                     $spoiler_note = str_repeat(
-                      _x( '&#183; ', 'Spoiler obfuscation character.', 'fictioneer' ), intval( strlen( $excerpt ) )
+                      _x( '&#183; ', 'Spoiler obfuscation character.', 'fictioneer' ), intval( mb_strlen( $excerpt ) )
                     );
                     $spoiler_note = apply_filters( 'fictioneer_filter_obfuscation_string', $spoiler_note, $post );
                   ?>
-                  <?php if ( strlen( str_replace( '…', '', $excerpt ) ) > 2 ) : ?>
+                  <?php if ( mb_strlen( str_replace( '…', '', $excerpt ) ) > 2 ) : ?>
                     <?php if ( ! $args['spoiler'] ) : ?>
                       <span data-click="toggle-obfuscation" tabindex="0">
                         <span class="obfuscated">&nbsp;<?php echo $spoiler_note; ?></span>
diff --git a/partials/_latest-updates-compact.php b/partials/_latest-updates-compact.php
index 86b8cbe6..94eb480d 100644
--- a/partials/_latest-updates-compact.php
+++ b/partials/_latest-updates-compact.php
@@ -210,7 +210,7 @@ remove_filter( 'posts_where', 'fictioneer_exclude_protected_posts' );
 
           // Chapter excerpt
           $chapter_excerpt = fictioneer_get_forced_excerpt( $chapter_list[0]->ID, 768 );
-          $show_excerpt = strlen( str_replace( '…', '', $chapter_excerpt ) ) > 2;
+          $show_excerpt = mb_strlen( str_replace( '…', '', $chapter_excerpt ) ) > 2;
 
           // Truncate factor
           $truncate_factor = $args['vertical'] ? '_2-2' : '_cq-1-2';