diff --git a/src/Extension/Attributes/Util/AttributesHelper.php b/src/Extension/Attributes/Util/AttributesHelper.php
index de5c111e1d..41171fae7e 100644
--- a/src/Extension/Attributes/Util/AttributesHelper.php
+++ b/src/Extension/Attributes/Util/AttributesHelper.php
@@ -23,7 +23,7 @@
  */
 final class AttributesHelper
 {
-    private const SINGLE_ATTRIBUTE = '\s*([.#][_a-z0-9-]+|' . RegexHelper::PARTIAL_ATTRIBUTENAME . RegexHelper::PARTIAL_ATTRIBUTEVALUESPEC . ')\s*';
+    private const SINGLE_ATTRIBUTE = '\s*([.]-?[_a-z]\S*|[#]\S+|' . RegexHelper::PARTIAL_ATTRIBUTENAME . RegexHelper::PARTIAL_ATTRIBUTEVALUESPEC . ')\s*';
     private const ATTRIBUTE_LIST   = '/^{:?(' . self::SINGLE_ATTRIBUTE . ')+}/i';
 
     /**
diff --git a/tests/functional/Extension/Attributes/data/class_names.html b/tests/functional/Extension/Attributes/data/class_names.html
new file mode 100644
index 0000000000..e92bcd308b
--- /dev/null
+++ b/tests/functional/Extension/Attributes/data/class_names.html
@@ -0,0 +1,6 @@
+<p class="some-class(value)">Some text</p>
+<p class="some-class(value)">Some text</p>
+<p class="-hello">Some text</p>
+<p class="smile-😎 some-class">Some text</p>
+<p id="smile-😎">Some text</p>
+<p id="smile-😎">Some text</p>
diff --git a/tests/functional/Extension/Attributes/data/class_names.md b/tests/functional/Extension/Attributes/data/class_names.md
new file mode 100644
index 0000000000..25ee4f5a5d
--- /dev/null
+++ b/tests/functional/Extension/Attributes/data/class_names.md
@@ -0,0 +1,17 @@
+{class="some-class(value)"}
+Some text
+
+{.some-class(value)}
+Some text
+
+{.-hello}
+Some text
+
+{.smile-😎 .some-class}
+Some text
+
+{id="smile-😎"}
+Some text
+
+{#smile-😎}
+Some text