diff --git a/filter.hs b/filter.hs
index d235966..0c9d6f6 100755
--- a/filter.hs
+++ b/filter.hs
@@ -1,6 +1,7 @@
 #!/usr/bin/env runhaskell
 -- filter.hs
 import Text.Pandoc.JSON
+    ( Block(CodeBlock), ToJSONFilter(toJSONFilter) )
 import qualified Data.Text.IO as TIO
 import qualified Data.Text as T