diff --git a/CHANGELOG.md b/CHANGELOG.md
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,3 +1,7 @@
+# hpqtypes-1.4.2 (2015-06-08)
+* use strict StateT for DBT
+* use catch in withTransaction only if it might be used
+
 # hpqtypes-1.4.1 (2015-05-15)
 * add support for json and jsonb sql types
 * add support for lazy ByteString and Text
diff --git a/hpqtypes.cabal b/hpqtypes.cabal
--- a/hpqtypes.cabal
+++ b/hpqtypes.cabal
@@ -1,5 +1,5 @@
 name:                hpqtypes
-version:             1.4.1
+version:             1.4.2
 synopsis:            Haskell bindings to libpqtypes
 
 description:         Efficient and easy-to-use bindings to (slightly modified)
diff --git a/src/Database/PostgreSQL/PQTypes/Internal/Monad.hs b/src/Database/PostgreSQL/PQTypes/Internal/Monad.hs
--- a/src/Database/PostgreSQL/PQTypes/Internal/Monad.hs
+++ b/src/Database/PostgreSQL/PQTypes/Internal/Monad.hs
@@ -13,11 +13,11 @@
 import Control.Monad.Catch
 import Control.Monad.Error.Class
 import Control.Monad.Reader.Class
-import Control.Monad.State
+import Control.Monad.State.Strict
 import Control.Monad.Trans.Control
 import Control.Monad.Writer.Class
 import Data.Monoid
-import qualified Control.Monad.Trans.State as S
+import qualified Control.Monad.Trans.State.Strict as S
 
 import Database.PostgreSQL.PQTypes.Class
 import Database.PostgreSQL.PQTypes.Internal.Connection
diff --git a/src/Database/PostgreSQL/PQTypes/Transaction.hs b/src/Database/PostgreSQL/PQTypes/Transaction.hs
--- a/src/Database/PostgreSQL/PQTypes/Transaction.hs
+++ b/src/Database/PostgreSQL/PQTypes/Transaction.hs
@@ -15,6 +15,7 @@
 
 import Control.Monad
 import Control.Monad.Catch
+import Data.Function
 import Data.String
 import Data.Typeable
 
@@ -76,30 +77,34 @@
 -- | Execute monadic action within a transaction using given transaction
 -- settings. Note that it won't work as expected if a transaction is already
 -- active (in such case 'withSavepoint' should be used instead).
-withTransaction' :: forall m a. (MonadDB m, MonadMask m)
+withTransaction' :: (MonadDB m, MonadMask m)
                  => TransactionSettings -> m a -> m a
-withTransaction' ts m = mask $ exec 1
+withTransaction' ts m = mask $ \restore -> (`fix` 1) $ \loop n -> do
+  -- Optimization for squashing possible space leaks.
+  -- It looks like GHC doesn't like 'catch' and passes
+  -- on introducing strictness in some cases.
+  let maybeRestart = case tsRestartPredicate ts of
+        Just _  -> handleJust (expred n) (\_ -> loop $ n+1)
+        Nothing -> id
+  maybeRestart $ do
+    begin' ts
+    res <- restore m `onException` rollback' ts
+    commit' ts
+    return res
   where
-    exec :: Integer -> (forall r. m r -> m r) -> m a
-    exec !n restore = handleJust expred (const $ exec (succ n) restore) $ do
-      begin' ts
-      res <- restore m `onException` rollback' ts
-      commit' ts
-      return res
-      where
-        expred :: SomeException -> Maybe ()
-        expred e = do
-          -- check if the predicate exists
-          RestartPredicate f <- tsRestartPredicate ts
-          -- cast exception to the type expected by the predicate
-          err <- msum [
-              -- either cast the exception itself...
-              fromException e
-              -- ...or extract it from DBException
-            , fromException e >>= \DBException{..} -> cast dbeError
-            ]
-          -- check if the predicate allows for the restart
-          guard $ f err n
+    expred :: Integer -> SomeException -> Maybe ()
+    expred !n e = do
+      -- check if the predicate exists
+      RestartPredicate f <- tsRestartPredicate ts
+      -- cast exception to the type expected by the predicate
+      err <- msum [
+          -- either cast the exception itself...
+          fromException e
+          -- ...or extract it from DBException
+        , fromException e >>= \DBException{..} -> cast dbeError
+        ]
+      -- check if the predicate allows for the restart
+      guard $ f err n
 
 -- | Begin transaction using given transaction settings.
 begin' :: MonadDB m => TransactionSettings -> m ()