diff --git a/Text/OPML/Types.hs b/Text/OPML/Types.hs
--- a/Text/OPML/Types.hs
+++ b/Text/OPML/Types.hs
@@ -54,7 +54,9 @@
 data Null deriving(Typeable)
 
 instance Predicate Null Text where
-  validate p value = unless (Text.null value) $ throwRefine $ RefineOtherException (typeOf p) "Text is not null"
+  validate p value = if not $ Text.null value
+    then pure $ RefineOtherException (typeOf p) "Text is not null"
+    else Nothing
 
 data OpmlHead = OpmlHead
   { opmlTitle       :: Text
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:             0.8.0.0
+version:             0.9.0.0
 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.
@@ -46,7 +46,7 @@
     , microlens
     , microlens-th
     , monoid-subclasses
-    , refined >= 0.2
+    , refined >= 0.5
     , semigroups
     , text
     , time >= 1.5
@@ -77,7 +77,7 @@
     , parsers
     , QuickCheck
     , quickcheck-instances
-    , refined >= 0.2
+    , refined >= 0.5
     , resourcet
     , semigroups
     , tasty
diff --git a/test/Arbitrary.hs b/test/Arbitrary.hs
--- a/test/Arbitrary.hs
+++ b/test/Arbitrary.hs
@@ -14,7 +14,7 @@
 import           Data.Char
 import           Data.List.NonEmpty
 import           Data.Maybe
-import           Data.Text                 as Text (Text, find, null, pack)
+import           Data.Text                 as Text (Text, find, pack)
 import           Data.Text.Encoding
 import           Data.Time.Clock
 import           Data.Tree
@@ -95,12 +95,7 @@
 genAlphaNum :: Gen Char
 genAlphaNum = oneof [choose('a', 'z'), suchThat arbitrary isDigit]
 
-instance Arbitrary (Refined (Not Null) Text) where
-  arbitrary = do
-    ~(Right t) <- refine <$> arbitrary `suchThat` (not . Text.null)
-    return t
 
-
 instance Arbitrary OpmlHead where
   arbitrary = OpmlHead <$> arbitrary
                        <*> (Just <$> genTime)
@@ -160,6 +155,6 @@
   root <- arbitrary
   degree <- choose (0, 100)
   case (n > 1, root) of
-    (True, OpmlOutlineGeneric _ _) -> Node <$> pure root <*> vectorOf degree (genOutlineTree (n-1))
+    (True, OpmlOutlineGeneric _ _)  -> Node <$> pure root <*> vectorOf degree (genOutlineTree (n-1))
     (False, OpmlOutlineGeneric _ _) -> return $ Node root []
-    _ -> return $ Node root []
+    _                               -> return $ Node root []