diff --git a/hkt.hs b/hkt.hs
--- a/hkt.hs
+++ b/hkt.hs
@@ -16,6 +16,7 @@
 -- You should have received a copy of the GNU Affero General Public License
 -- along with this program.  If not, see <http://www.gnu.org/licenses/>.
 
+{-# LANGUAGE CPP #-}
 {-# LANGUAGE DeriveGeneric #-}
 
 import HOpenPGP.Tools.Common (banner, versioner, warranty, keyMatchesFingerprint, keyMatchesEightOctetKeyId, keyMatchesUIDSubString)
@@ -26,7 +27,10 @@
 import Codec.Encryption.OpenPGP.Serialize ()
 import Codec.Encryption.OpenPGP.Signatures (verifyTKWith, verifySigWith, verifyAgainstKeyring)
 import Codec.Encryption.OpenPGP.Types
-import Control.Applicative ((<$>),(<*>), optional, (<|>), pure)
+#if !MIN_VERSION_base(4,8,0)
+import Control.Applicative ((<$>),(<*>), pure)
+#endif
+import Control.Applicative (optional, (<|>))
 import Control.Arrow ((&&&))
 import Control.Lens ((^.), _1, _2, (^..))
 import Control.Monad.Trans.Resource (runResourceT, MonadResource)
@@ -57,12 +61,17 @@
 import Data.Map (Map)
 import qualified Data.Map as Map
 import Data.Maybe (fromMaybe, mapMaybe, listToMaybe)
-import Data.Monoid ((<>), mconcat)
+#if !MIN_VERSION_base(4,8,0)
+import Data.Monoid (mconcat)
+#endif
+import Data.Monoid ((<>))
 import Data.Text (Text)
 import qualified Data.Text as T
 import qualified Data.Text.Lazy.IO as TLIO
 import Data.Time.Clock.POSIX (getPOSIXTime, posixSecondsToUTCTime)
+#if !MIN_VERSION_base(4,8,0)
 import Data.Traversable (traverse)
+#endif
 import Data.Tuple (swap)
 import qualified Data.Yaml as Y
 import GHC.Generics
@@ -119,7 +128,7 @@
                    <*> show . _pkalgo
                    <*> pkalgoAbbrev . _pkalgo
                    <*> either (const "unknown") (show . pretty) . eightOctetKeyID
-                   <*> show . fingerprint
+                   <*> show . pretty . fingerprint
 
 showTKey :: TKey -> IO ()
 showTKey key = putDoc $
diff --git a/hokey.hs b/hokey.hs
--- a/hokey.hs
+++ b/hokey.hs
@@ -16,21 +16,25 @@
 -- You should have received a copy of the GNU Affero General Public License
 -- along with this program.  If not, see <http://www.gnu.org/licenses/>.
 
-{-# LANGUAGE DeriveFunctor, DeriveGeneric, FlexibleInstances #-}
+{-# LANGUAGE CPP #-}
+{-# LANGUAGE DeriveFunctor #-}
+{-# LANGUAGE DeriveGeneric #-}
+{-# LANGUAGE FlexibleInstances #-}
 
 import HOpenPGP.Tools.Common (banner, versioner, warranty)
 import HOpenPGP.Tools.HKP (fetchKeys, FetchValidationMethod(..), rearmorKeys)
 import HOpenPGP.Tools.TKUtils (processTK)
-import qualified Codec.Encryption.OpenPGP.ASCIIArmor as AA
 import Codec.Encryption.OpenPGP.Expirations (getKeyExpirationTimesFromSignature)
 import Codec.Encryption.OpenPGP.Fingerprint (fingerprint, eightOctetKeyID)
 import Codec.Encryption.OpenPGP.KeyInfo (pubkeySize, pkalgoAbbrev)
 import Codec.Encryption.OpenPGP.KeySelection (parseFingerprint)
+import Codec.Encryption.OpenPGP.Ontology (isCertRevocationSig, isCT, isKUF, isPHA, isPKBindingSig, isSKBindingSig)
 import Codec.Encryption.OpenPGP.Serialize ()
-import Codec.Encryption.OpenPGP.Signatures (verifyTKWith, verifySigWith, verifyAgainstKeys)
 import Codec.Encryption.OpenPGP.Types
+#if !MIN_VERSION_base(4,8,0)
 import Control.Applicative ((<$>),(<*>), pure)
-import Control.Arrow ((***), second)
+#endif
+import Control.Arrow ((***))
 import Control.Error.Util (hush)
 import Control.Lens ((^.), (&), _1, _2, mapped, over)
 import Control.Monad.Trans.Except (runExceptT)
@@ -52,7 +56,10 @@
 import Data.List (elemIndex, findIndex, nub, sort, sortBy, intercalate)
 import qualified Data.Map as Map
 import Data.Maybe (fromMaybe, mapMaybe, listToMaybe)
-import Data.Monoid ((<>), mconcat, Monoid(..))
+#if !MIN_VERSION_base(4,8,0)
+import Data.Monoid (mconcat, Monoid(..))
+#endif
+import Data.Monoid ((<>))
 import Data.Ord (comparing, Down(..))
 import qualified Data.Set as Set
 import Data.Text (Text)
@@ -190,12 +197,8 @@
             | otherwise = Nothing
         phas (SigV4 _ _ _ xs _ _ _) = colorizePHAs . concatMap (\(SigSubPacket _ (PreferredHashAlgorithms x)) -> x) $ filter isPHA xs
         phas _ = Colored Nothing Nothing []
-        isPHA (SigSubPacket _ (PreferredHashAlgorithms _)) = True
-        isPHA _ = False
         has = map (colorizeHA . hashAlgo) . alleged
         colorizeHA ha = uncurry Colored (if ha `elem` [DeprecatedMD5, SHA1] then (Just Red, Just "weak hash algorithm") else (Nothing, Nothing)) ha
-        isCT (SigSubPacket _ (SigCreationTime _)) = True
-        isCT _ = False
         sigcts (SigV4 _ _ _ xs _ _ _) = map (\(SigSubPacket _ (SigCreationTime x)) -> x) $ filter isCT xs
         alleged = filter (\x -> ((==) <$> sigissuer x <*> eoki (key^.tkKey._1)) == Just True)
         uatspsToText = T.pack . uatspsToString
@@ -223,15 +226,11 @@
             | not ('<' `elem` T.unpack u) = Colored (Just Yellow) (Just "no left angle bracket in uid")  -- FIXME: be more discerning
             | otherwise = Colored Nothing Nothing
         findRevocationReason = concatMap grabReasons . filter isCertRevocationSig
-        isCertRevocationSig (SigV4 CertRevocationSig _ _ _ _ _ _) = True
-        isCertRevocationSig _ = False
         grabReasons (SigV4 CertRevocationSig _ _ has _ _ _) = mapMaybe (grabReasons' . _sspPayload) has
         grabReasons _ = []
         grabReasons' (ReasonForRevocation a b) = Just (RevocationStatus True (show a) b)
         grabReasons' _ = Nothing
         kufs s = map (colorizeKUFs s . (\(SigSubPacket _ (KeyFlags x)) -> x) . maybe undefined id . find isKUF . hasheds) . newestWith (any isKUF . hasheds)
-        isKUF (SigSubPacket _ (KeyFlags _)) = True
-        isKUF _ = False
         colorizeKUFs False x = uncurry Colored (if (Set.member EncryptStorageKey x || Set.member EncryptCommunicationsKey x) && (Set.member SignDataKey x || Set.member CertifyKeysKey x) then (Just Yellow, Just "both signing & encryption") else (Just Green, Nothing)) x
         colorizeKUFs True x = uncurry Colored (if (Set.member CertifyKeysKey x) then (Just Red, Just "certification-capable subkey") else (if (Set.member EncryptStorageKey x || Set.member EncryptCommunicationsKey x) && Set.member SignDataKey x then (Just Yellow, Just "both signing & encryption") else (Just Green, Nothing))) x
         newestWith p = take 1 . sortBy (comparing (Down . take 1 . sigcts)) . filter p -- FIXME: this is terrible
@@ -250,10 +249,6 @@
         , skCrossCerts = CrossCertReport (Colored Nothing Nothing False) []
         }
         hasEncryptionCapableSubkey skrs = if any ((\x -> Set.member EncryptStorageKey x || Set.member EncryptCommunicationsKey x) . decolorize) skrs then Colored (Just Green) Nothing True else Colored (Just Red) (Just "no encryption-capable subkey present") False
-        isSKBindingSig (SigV4 SubkeyBindingSig _ _ _ _ _ _) = True
-        isSKBindingSig _ = False
-        isPKBindingSig (SigV4 PrimaryKeyBindingSig _ _ _ _ _ _) = True
-        isPKBindingSig _ = False
         embeddedSigs = filter isPKBindingSig . concatMap getEmbeds . filter isSKBindingSig
         getEmbeds (SigV4 _ _ _ _ xs _ _) = concatMap getEmbed xs
         getEmbeds _ = []
diff --git a/hopenpgp-tools.cabal b/hopenpgp-tools.cabal
--- a/hopenpgp-tools.cabal
+++ b/hopenpgp-tools.cabal
@@ -1,5 +1,5 @@
 name:                hopenpgp-tools
-version:             0.19
+version:             0.19.1
 synopsis:            hOpenPGP-based command-line tools
 description:         command-line tools for performing some OpenPGP-related operations
 homepage:            http://floss.scru.org/hopenpgp-tools
@@ -62,7 +62,7 @@
                ,       cryptohash             >= 0.7.7
                ,       directory
                ,       errors
-               ,       hOpenPGP               >= 2.4.1
+               ,       hOpenPGP               >= 2.5
                ,       http-client
                ,       http-client-tls
                ,       http-types
@@ -126,4 +126,4 @@
 source-repository this
   type:     git
   location: git://git.debian.org/users/clint/hopenpgp-tools.git
-  tag:      hopenpgp-tools/0.19
+  tag:      hopenpgp-tools/0.19.1
diff --git a/hot.hs b/hot.hs
--- a/hot.hs
+++ b/hot.hs
@@ -18,6 +18,8 @@
 -- You should have received a copy of the GNU Affero General Public License
 -- along with this program.  If not, see <http://www.gnu.org/licenses/>.
 
+{-# LANGUAGE CPP #-}
+
 import Paths_hopenpgp_tools (version)
 import HOpenPGP.Tools.Common (banner, versioner, warranty, prependAuto)
 import HOpenPGP.Tools.Parser (parsePExp)
@@ -25,7 +27,10 @@
 import Codec.Encryption.OpenPGP.ASCIIArmor.Types (Armor(..), ArmorType(..))
 import Codec.Encryption.OpenPGP.Serialize ()
 import Codec.Encryption.OpenPGP.Types
-import Control.Applicative ((<$>), (<*>), optional, pure)
+#if !MIN_VERSION_base(4,8,0)
+import Control.Applicative ((<$>), (<*>))
+#endif
+import Control.Applicative (optional)
 import Control.Error.Util (note)
 import Control.Monad.IO.Class (MonadIO, liftIO)
 import Control.Monad.Trans.Resource (runResourceT)