diff --git a/CHANGELOG.md b/CHANGELOG.md
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,3 +1,7 @@
+# hpqtypes-extras-1.6.2.0 (2018-07-11)
+* Support hpqtypes-1.6.0.0.
+* Drop support for GHC < 8.
+
 # hpqtypes-extras-1.6.1.0 (2018-03-18)
 * Add support for GHC 8.4.1.
 * Drop support for GHC 7.8.
diff --git a/hpqtypes-extras.cabal b/hpqtypes-extras.cabal
--- a/hpqtypes-extras.cabal
+++ b/hpqtypes-extras.cabal
@@ -1,5 +1,5 @@
 name:                hpqtypes-extras
-version:             1.6.1.0
+version:             1.6.2.0
 synopsis:            Extra utilities for hpqtypes library
 description:         The following extras for hpqtypes library:
                      .
@@ -20,8 +20,7 @@
 category:            Database
 build-type:          Simple
 cabal-version:       >=1.10
-tested-with:         GHC == 7.10.3, GHC == 8.0.2,
-                     GHC == 8.2.2, GHC == 8.4.1
+tested-with:         GHC == 8.0.2, GHC == 8.2.2, GHC == 8.4.3
 
 Source-repository head
   Type:     git
@@ -51,8 +50,8 @@
   other-modules:   Database.PostgreSQL.PQTypes.Checks.Util
                  , Database.PostgreSQL.PQTypes.Utils.NubList
 
-  build-depends: base < 5
-               , hpqtypes >= 1.5.2.0
+  build-depends: base > 4 && < 5
+               , hpqtypes >= 1.6.0.0
                , base16-bytestring
                , bytestring
                , containers
diff --git a/src/Database/PostgreSQL/PQTypes/Model/ColumnType.hs b/src/Database/PostgreSQL/PQTypes/Model/ColumnType.hs
--- a/src/Database/PostgreSQL/PQTypes/Model/ColumnType.hs
+++ b/src/Database/PostgreSQL/PQTypes/Model/ColumnType.hs
@@ -1,3 +1,4 @@
+{-# LANGUAGE TypeApplications #-}
 module Database.PostgreSQL.PQTypes.Model.ColumnType (
     ColumnType(..)
   , columnTypeToSQL
@@ -30,7 +31,7 @@
     deriving (Eq, Ord, Show)
 
 instance PQFormat ColumnType where
-  pqFormat = const $ pqFormat (undefined::T.Text)
+  pqFormat = pqFormat @T.Text
 instance FromSQL ColumnType where
   type PQBase ColumnType = PQBase T.Text
   fromSQL mbase = parseType . T.toLower <$> fromSQL mbase