diff --git a/tests/HTMLPurifier/HTMLDefinitionTest.php b/tests/HTMLPurifier/HTMLDefinitionTest.php
index 56d680f8..3e8a1da7 100644
--- a/tests/HTMLPurifier/HTMLDefinitionTest.php
+++ b/tests/HTMLPurifier/HTMLDefinitionTest.php
@@ -222,6 +222,17 @@ public function test_AllowedAttributes_multipleErrors()
         $this->assertPurification_AllowedAttributes_local_p_style();
     }
 
+    public function test_AllowedAttributes_invalidAttributeDueToConsistingOfNumbers_UsingDirectLex()
+    {
+        $this->config->set('HTML.AllowedElements', array('a'));
+        $this->config->set('HTML.AllowedAttributes', 'href');
+        $this->config->set('Core.LexerImpl', 'DirectLex');
+        $this->assertPurification(
+            '<a href="https://example.com/" 10="hoge">Test</a>',
+            '<a href="https://example.com/">Test</a>'
+        );
+    }
+
     public function test_ForbiddenElements()
     {
         $this->config->set('HTML.ForbiddenElements', 'b');