diff --git a/ChangeLog.md b/ChangeLog.md
--- a/ChangeLog.md
+++ b/ChangeLog.md
@@ -1,5 +1,9 @@
 <!-- -*- Markdown -*- -->
 
+## 0.8.0.4
+
+- Drop unused pragma.
+
 ## 0.8.0.3
 
 - Drop unreferenced overloading.
diff --git a/relational-query.cabal b/relational-query.cabal
--- a/relational-query.cabal
+++ b/relational-query.cabal
@@ -1,5 +1,5 @@
 name:                relational-query
-version:             0.8.0.3
+version:             0.8.0.4
 synopsis:            Typeful, Modular, Relational, algebraic query engine
 description:         This package contiains typeful relation structure and
                      relational-algebraic query building DSL which can
diff --git a/src/Database/Relational/Query/Constraint.hs b/src/Database/Relational/Query/Constraint.hs
--- a/src/Database/Relational/Query/Constraint.hs
+++ b/src/Database/Relational/Query/Constraint.hs
@@ -1,7 +1,6 @@
 {-# LANGUAGE MultiParamTypeClasses #-}
 {-# LANGUAGE FlexibleInstances #-}
 {-# LANGUAGE FlexibleContexts #-}
-{-# LANGUAGE UndecidableInstances #-}
 
 -- |
 -- Module      : Database.Relational.Query.Constraint