diff --git a/lib/gitlab/markdown/reference_filter.rb b/lib/gitlab/markdown/reference_filter.rb
index 4e936d7cd5..9b293c957d 100644
--- a/lib/gitlab/markdown/reference_filter.rb
+++ b/lib/gitlab/markdown/reference_filter.rb
@@ -70,7 +70,7 @@ module Gitlab
       end
 
       def reference_class(type)
-        "gfm gfm-#{type}".strip
+        "gfm gfm-#{type}"
       end
 
       # Iterate through the document's text nodes, yielding the current node's