diff --git a/langfilter/Main.hs b/langfilter/Main.hs
index b7d2209..71389de 100644
--- a/langfilter/Main.hs
+++ b/langfilter/Main.hs
@@ -39,7 +39,7 @@ makeBlocks :: Block -> [Block]
 makeBlocks (Div ("", clss, []) blks)
   | Just (cls, rest) <- pluck1 ["figure", "aside"] clss =
       let html  = RawBlock $ Format "html"
-          open  = html $ "<" <> cls <> "class='" <> Text.unwords rest <> "'>"
+          open  = html $ "<" <> cls <> " class='" <> Text.unwords rest <> "'>"
           close = html $ "</" <> cls <> ">"
       in
       [open] ++ blks ++ [close]