diff --git a/app/assets/javascripts/pretty-text/engines/discourse-markdown/bbcode-block.js.es6 b/app/assets/javascripts/pretty-text/engines/discourse-markdown/bbcode-block.js.es6
index ddb92eefdb1..ce9d468d486 100644
--- a/app/assets/javascripts/pretty-text/engines/discourse-markdown/bbcode-block.js.es6
+++ b/app/assets/javascripts/pretty-text/engines/discourse-markdown/bbcode-block.js.es6
@@ -51,6 +51,8 @@ export function parseBBCodeTag(src, start, max, multiline) {
         return;
       }
 
+      tag = tag.toLowerCase();
+
       return {tag, length: tag.length+3, closing: true};
     }
     return;