diff --git a/src/Extension/HeadingPermalink/Slug/DefaultSlugGenerator.php b/src/Extension/HeadingPermalink/Slug/DefaultSlugGenerator.php
index 6207da0b5d..65c920f94e 100644
--- a/src/Extension/HeadingPermalink/Slug/DefaultSlugGenerator.php
+++ b/src/Extension/HeadingPermalink/Slug/DefaultSlugGenerator.php
@@ -24,8 +24,8 @@ public function createSlug(string $input): string
         $slug = \mb_strtolower($slug);
         // Try replacing whitespace with a dash
         $slug = \preg_replace('/\s+/u', '-', $slug) ?? $slug;
-        // Try removing non-alphanumeric and non-dash characters
-        $slug = \preg_replace('/[^\p{Lu}\p{Ll}\p{Lt}\p{Nd}\p{Nl}\-]/u', '', $slug) ?? $slug;
+        // Try removing characters other than letters, numbers, and marks.
+        $slug = \preg_replace('/[^\p{L}\p{Nd}\p{Nl}\p{M}-]+/u', '', $slug) ?? $slug;
 
         return $slug;
     }
diff --git a/tests/unit/Extension/HeadingPermalink/Slug/DefaultSlugGeneratorTest.php b/tests/unit/Extension/HeadingPermalink/Slug/DefaultSlugGeneratorTest.php
index 08847f29b3..f892408011 100644
--- a/tests/unit/Extension/HeadingPermalink/Slug/DefaultSlugGeneratorTest.php
+++ b/tests/unit/Extension/HeadingPermalink/Slug/DefaultSlugGeneratorTest.php
@@ -49,5 +49,15 @@ public function dataProviderForTestCreateSlug()
         yield ['ŤĘŜŦ', 'ťęŝŧ'];
 
         yield ["\nWho\nput\n\n newlines  \nin here?!\n", 'who-put-newlines-in-here'];
+
+        yield ['අත්හදා බලන මාතෘකාව',    'අත්හදා-බලන-මාතෘකාව'];
+        yield ['අත්හදා බලන මාතෘකාව -',  'අත්හදා-බලන-මාතෘකාව--'];
+        yield ['අත්හදා බලන මාතෘකාව - ', 'අත්හදා-බලන-මාතෘකාව--'];
+        yield ['අත්හදා බලන මාතෘකාව - අ', 'අත්හදා-බලන-මාතෘකාව---අ'];
+
+        yield ['测试标题',     '测试标题'];
+        yield ['测试 # 标题',  '测试--标题'];
+        yield ['测试 x² 标题', '测试-x-标题'];
+        yield ['試験タイトル', '試験タイトル'];
     }
 }