diff --git a/squeal-postgresql-ltree.cabal b/squeal-postgresql-ltree.cabal
--- a/squeal-postgresql-ltree.cabal
+++ b/squeal-postgresql-ltree.cabal
@@ -1,6 +1,6 @@
 cabal-version: 2.2
 name: squeal-postgresql-ltree
-version: 0.1.0.1
+version: 0.1.0.2
 synopsis: LTree extension for Squeal
 description: LTree extension for Squeal
 homepage: https://github.com/morphismtech/squeal/ltree
diff --git a/src/Squeal/PostgreSQL/LTree.hs b/src/Squeal/PostgreSQL/LTree.hs
--- a/src/Squeal/PostgreSQL/LTree.hs
+++ b/src/Squeal/PostgreSQL/LTree.hs
@@ -45,7 +45,8 @@
   ) where
 
 import Control.Exception hiding (TypeError)
-import Control.Monad.Reader
+import Control.Monad (when)
+import Control.Monad.Reader (ReaderT(ReaderT))
 import Data.String
 import Data.Text
 import GHC.Generics