diff --git a/GenerateC.hs b/GenerateC.hs
index 1fdbd09..ab3cdd1 100644
--- a/GenerateC.hs
+++ b/GenerateC.hs
@@ -265,7 +265,7 @@ cgenTopLevel ops p
           tell ["void tock_main (Process *me, Channel *in, Channel *out, Channel *err) {\n"]
           genName name
           tell [" (me"]
-          sequence_ [tell [", "] >> call genTLPChannel ops c | c <- chans]
+          sequence_ [tell [", "] >> call genTLPChannel ops c | (_,c) <- chans]
           tell [");\n"]
           tell ["}\n"]
 --}}}
diff --git a/GenerateCPPCSP.hs b/GenerateCPPCSP.hs
index 60d6066..403c367 100644
--- a/GenerateCPPCSP.hs
+++ b/GenerateCPPCSP.hs
@@ -143,8 +143,16 @@ cppgenTopLevel ops p
           tell [" csp::Run( csp::InParallel (new StreamWriter(std::cout,out.reader())) (new StreamWriter(std::cerr,err.reader())) (csp::InSequenceOneThread ( new proc_"]
           genName name 
           tell ["("]
-          infixComma [tell ["&"] >> call genTLPChannel ops c | c <- chans]
+          infixComma $ map (tlpChannel ops) chans
           tell [")) (new csp::common::ChannelPoisoner< csp::Chanout<uint8_t>/**/> (out.writer())) (new csp::common::ChannelPoisoner< csp::Chanout<uint8_t>/**/> (err.writer()))   ) ); csp::End_CPPCSP(); return 0;}"]
+  where
+    tlpChannel :: GenOps -> (A.Direction,TLPChannel) -> CGen()
+    tlpChannel ops (dir,c) = case dir of
+                               A.DirUnknown -> tell ["&"] >> chanName
+                               A.DirInput -> chanName >> tell [" .reader() "]
+                               A.DirOutput -> chanName >> tell [" .writer() "]
+                             where
+                               chanName = call genTLPChannel ops c
 
 --}}}
 
diff --git a/TLP.hs b/TLP.hs
index 284c978..3552752 100644
--- a/TLP.hs
+++ b/TLP.hs
@@ -36,7 +36,7 @@ data TLPChannel = TLPIn | TLPOut | TLPError
 
 -- | Get the name of the TLP and the channels it uses.
 -- Fail if the process isn't using a valid interface.
-tlpInterface :: (CSM m, Die m) => m (A.Name, [TLPChannel])
+tlpInterface :: (CSM m, Die m) => m ( A.Name, [(A.Direction, TLPChannel)] )
 tlpInterface
     =  do ps <- get
           when (null $ csMainLocals ps) (die "No main process found")
@@ -46,17 +46,17 @@ tlpInterface
                        A.Proc _ _ fs _ -> return fs
                        _ -> die "Last definition is not a PROC"
           chans <- mapM tlpChannel formals
-          when ((nub chans) /= chans) $ die "Channels used more than once in TLP"
+          when ((nub (map snd chans)) /= (map snd chans)) $ die "Channels used more than once in TLP"
           return (mainName, chans)
   where
-    tlpChannel :: (CSM m, Die m) => A.Formal -> m TLPChannel
+    tlpChannel :: (CSM m, Die m) => A.Formal -> m (A.Direction, TLPChannel)
     tlpChannel (A.Formal _ (A.Chan dir _ A.Byte) n)
         =  do def <- lookupName n
               let origN = A.ndOrigName def
               case lookup origN tlpChanNames of
                 Just c ->
                   if (dir == A.DirUnknown || dir == (tlpDir c))
-                    then return c
+                    then return (dir,c)
                     else die $ "TLP formal " ++ show n ++ " has wrong direction for its name"
                 _ -> die $ "TLP formal " ++ show n ++ " has unrecognised name"
     tlpChannel (A.Formal _ _ n)