diff --git a/Database/Sql/Simple/PostgreSQL.hs b/Database/Sql/Simple/PostgreSQL.hs
--- a/Database/Sql/Simple/PostgreSQL.hs
+++ b/Database/Sql/Simple/PostgreSQL.hs
@@ -7,7 +7,7 @@
 {-# LANGUAGE CPP #-}
 
 module Database.Sql.Simple.PostgreSQL
-    ( PostgreSQL
+    ( PostgreSQL(..)
     , ConnectInfo(..)
     , postgreSQL
     , psql
@@ -70,6 +70,7 @@
     fold  (PostgreSQL c) q = PSql.fold  c (psqlQuery q)
     fold_ (PostgreSQL c) q = PSql.fold_ c (psqlQuery q)
 
+instance Transaction PostgreSQL where
     begin    (PostgreSQL c) = Sql $ PSql.begin c
     commit   (PostgreSQL c) = Sql $ PSql.commit c
     rollback (PostgreSQL c) = Sql $ PSql.rollback c
diff --git a/sql-simple-postgresql.cabal b/sql-simple-postgresql.cabal
--- a/sql-simple-postgresql.cabal
+++ b/sql-simple-postgresql.cabal
@@ -1,5 +1,5 @@
 name:                sql-simple-postgresql
-version:             0.2.1
+version:             0.3.0
 synopsis:            postgresql backend for sql-simple
 -- description:         
 license:             MIT
@@ -17,7 +17,7 @@
   exposed-modules:     Database.Sql.Simple.PostgreSQL
   build-depends:       base                 >=4.6 && <4.8
                      , text                 >=1.1 && <1.2
-                     , sql-simple           >=0.2 && <0.3
+                     , sql-simple           >=0.3 && <0.4
                      , postgresql-simple    >=0.4 && <0.5
                      , data-default-class   >=0.0 && <0.1