diff --git a/opml-conduit.cabal b/opml-conduit.cabal
--- a/opml-conduit.cabal
+++ b/opml-conduit.cabal
@@ -1,5 +1,5 @@
 name:                opml-conduit
-version:             0.4.0.0
+version:             0.4.0.1
 synopsis:            Streaming parser/renderer for the OPML 2.0 format.
 description:
     This library implements the OPML 2.0 standard (<http://dev.opml.org/spec2.html>) as a 'conduit' parser/renderer.
diff --git a/test/Arbitrary.hs b/test/Arbitrary.hs
--- a/test/Arbitrary.hs
+++ b/test/Arbitrary.hs
@@ -90,8 +90,8 @@
 
 -- | Generates 'OutlineBase''s categories.
 -- This generator makes sure that the result has no @,@ nor @/@ characters, since those are used as separators.
-instance Arbitrary [NonEmpty (NonNull Text)] where
-  arbitrary = listOf genCategoryPath
+instance Arbitrary (NonEmpty (NonNull Text)) where
+  arbitrary = genCategoryPath
     where genCategory = genNonNull `suchThat` (isNothing . find (\c -> c == ',' || c == '/') . toNullable)
           genCategoryPath = (:|) <$> genCategory <*> listOf genCategory
   -- shrink = genericShrink