diff --git a/Control/Monad/Trans/Except.hs b/Control/Monad/Trans/Except.hs
--- a/Control/Monad/Trans/Except.hs
+++ b/Control/Monad/Trans/Except.hs
@@ -45,6 +45,7 @@
     handleE,
     tryE,
     finallyE,
+    onE,
     -- * Lifting other operations
     liftCallCC,
     liftListen,
@@ -328,6 +329,14 @@
     closer
     either throwE return res
 {-# INLINE finallyE #-}
+
+-- | If the first action succeeds, return its value, ignoring the
+-- second action.  If the first action throws an exception, run the
+-- second action and then throw an exception, either the one thrown by
+-- the second action, if any, or the one thrown by the first action.
+onE :: (Monad m) => ExceptT e m a -> ExceptT e m b -> ExceptT e m a
+onE action1 action2 = action1 `catchE` \ e -> action2 >> throwE e
+{-# INLINE onE #-}
 
 -- | Lift a @callCC@ operation to the new monad.
 liftCallCC :: CallCC m (Either e a) (Either e b) -> CallCC (ExceptT e m) a b
diff --git a/Control/Monad/Trans/State/Lazy.hs b/Control/Monad/Trans/State/Lazy.hs
--- a/Control/Monad/Trans/State/Lazy.hs
+++ b/Control/Monad/Trans/State/Lazy.hs
@@ -64,6 +64,9 @@
     liftCatch,
     liftListen,
     liftPass,
+    -- * Conversion to and from the strict version
+    strictToLazyStateT,
+    lazyToStrictStateT,
     -- * Examples
     -- ** State monads
     -- $examples
@@ -78,6 +81,7 @@
 import Control.Monad.IO.Class
 import Control.Monad.Signatures
 import Control.Monad.Trans.Class
+import qualified Control.Monad.Trans.State.Strict as Strict
 #if MIN_VERSION_base(4,12,0)
 import Data.Functor.Contravariant
 #endif
@@ -357,6 +361,16 @@
     ~((a, f), s') <- runStateT m s
     return ((a, s'), f)
 {-# INLINE liftPass #-}
+
+-- | Convert from the strict version to the lazy version
+strictToLazyStateT :: Strict.StateT s m a -> StateT s m a
+strictToLazyStateT (Strict.StateT f) = StateT f
+{-# INLINE strictToLazyStateT #-}
+
+-- | Convert from the lazy version to the strict version
+lazyToStrictStateT :: StateT s m a -> Strict.StateT s m a
+lazyToStrictStateT (StateT f) = Strict.StateT f
+{-# INLINE lazyToStrictStateT #-}
 
 {- $examples
 
diff --git a/changelog b/changelog
--- a/changelog
+++ b/changelog
@@ -1,5 +1,9 @@
 -*-change-log-*-
 
+0.6.3.0 Ross Paterson <R.Paterson@city.ac.uk> Jan 2026
+	* Add Control.Monad.Trans.Except.onE
+	* Add strictToLazyState and lazyToStrictStateT
+
 0.6.2.0 Ross Paterson <R.Paterson@city.ac.uk> Apr 2025
 	* Redefine runAccumT, runExceptT and runSelectT as fields
 	* Document strictness of some transformers
diff --git a/transformers.cabal b/transformers.cabal
--- a/transformers.cabal
+++ b/transformers.cabal
@@ -1,5 +1,5 @@
 name:         transformers
-version:      0.6.2.0
+version:      0.6.3.0
 license:      BSD3
 license-file: LICENSE
 author:       Andy Gill, Ross Paterson