diff --git a/lib/lexer_block/htmlblock.js b/lib/lexer_block/htmlblock.js
index c631e52..1c92de5 100644
--- a/lib/lexer_block/htmlblock.js
+++ b/lib/lexer_block/htmlblock.js
@@ -51,7 +51,7 @@ module.exports = function htmlblock(state, startLine, endLine, silent) {
       if (!match) { return false; }
     }
     // Make sure tag name is valid
-    if (block_names.indexOf(match[1]) < 0) { return false; }
+    if (block_names.indexOf(match[1].toLowerCase()) < 0) { return false; }
     if (silent) { return true; }
 
   } else {