diff --git a/Michelf/Markdown.php b/Michelf/Markdown.php
index 3af20b5..4f08222 100644
--- a/Michelf/Markdown.php
+++ b/Michelf/Markdown.php
@@ -1531,7 +1531,7 @@ class Markdown implements MarkdownInterface {
 # one.
 #
 
-class _MarkdownExtra_TmpImpl extends \Michelf\Markdown {
+abstract class _MarkdownExtra_TmpImpl extends \Michelf\Markdown {
 
 	### Configuration Variables ###