diff --git a/Control/Arrow/Reader.hs b/Control/Arrow/Reader.hs
--- a/Control/Arrow/Reader.hs
+++ b/Control/Arrow/Reader.hs
@@ -38,6 +38,14 @@
   ReaderT f <+> ReaderT g = ReaderT (f <+> g);
 };
 
+instance (ArrowChoice s) => ArrowChoice (ReaderT r s) where {
+  left (ReaderT x) = ReaderT $ let {
+                       f :: (Either a b, r) -> Either (a, r) b;
+                       f (Left  x, r) = Left (x, r);
+                       f (Right y, r) = Right y;
+                     } in arr f >>> left x;
+};
+
 instance (ArrowLoop s) => ArrowLoop (ReaderT r s) where {
   loop = ReaderT . loop . (<<< swap_snds_A) . runReaderT;
 };
diff --git a/Control/Arrow/Writer.hs b/Control/Arrow/Writer.hs
--- a/Control/Arrow/Writer.hs
+++ b/Control/Arrow/Writer.hs
@@ -41,6 +41,13 @@
   WriterT f <+> WriterT g = WriterT (f <+> g);
 };
 
+instance (Monoid w, ArrowChoice r) => ArrowChoice (WriterT w r) where {
+  left (WriterT x) = WriterT $ let {
+                       f (Left (x, w)) = (Left x, w);
+                       f (Right y)     = (Right y, mempty);
+                     } in left x >>> arr f;
+};
+
 instance (Monoid w, ArrowLoop r) => ArrowLoop (WriterT w r) where {
   loop = WriterT . loop . (>>> swap_snds_A) . runWriterT;
 };
diff --git a/atl.cabal b/atl.cabal
--- a/atl.cabal
+++ b/atl.cabal
@@ -1,5 +1,5 @@
 Name:atl
-Version:15322.2
+Version:15409.1
 Description:Arrow Transformer Library
 License:LGPL
 License-File:license.txt