diff --git a/Parsedown.php b/Parsedown.php
index f5dd0fa..757666e 100644
--- a/Parsedown.php
+++ b/Parsedown.php
@@ -683,7 +683,7 @@ class Parsedown
             return;
         }
 
-        if (preg_match('/^<(\w*)(?:[ ]*'.$this->regexHtmlAttribute.')*[ ]*(\/)?>/', $Line['text'], $matches))
+        if (preg_match('/^<(\w[\w-]*)(?:[ ]*'.$this->regexHtmlAttribute.')*[ ]*(\/)?>/', $Line['text'], $matches))
         {
             $element = strtolower($matches[1]);
 
@@ -1268,7 +1268,7 @@ class Parsedown
             return;
         }
 
-        if ($Excerpt['text'][1] === '/' and preg_match('/^<\/\w*[ ]*>/s', $Excerpt['text'], $matches))
+        if ($Excerpt['text'][1] === '/' and preg_match('/^<\/\w[\w-]*[ ]*>/s', $Excerpt['text'], $matches))
         {
             return array(
                 'markup' => $matches[0],
@@ -1284,7 +1284,7 @@ class Parsedown
             );
         }
 
-        if ($Excerpt['text'][1] !== ' ' and preg_match('/^<\w*(?:[ ]*'.$this->regexHtmlAttribute.')*[ ]*\/?>/s', $Excerpt['text'], $matches))
+        if ($Excerpt['text'][1] !== ' ' and preg_match('/^<\w[\w-]*(?:[ ]*'.$this->regexHtmlAttribute.')*[ ]*\/?>/s', $Excerpt['text'], $matches))
         {
             return array(
                 'markup' => $matches[0],