diff --git a/Main.hs b/Main.hs
index 1198774..6a686d7 100644
--- a/Main.hs
+++ b/Main.hs
@@ -453,8 +453,10 @@ postCAnalyse :: String -> ((Handle, Handle), String) -> PassM ()
 postCAnalyse fn ((outHandle, _), _)
     =  do asm <- liftIO $ readFile fn
 
+          names <- needStackSizes
+
           progress "Analysing assembly"
-          output <- analyseAsm asm
+          output <- analyseAsm (Just $ map A.nameName names) asm
 
           liftIO $ hPutStr outHandle output
 
diff --git a/backends/AnalyseAsm.hs b/backends/AnalyseAsm.hs
index 3eb6a0e..7e51b9c 100644
--- a/backends/AnalyseAsm.hs
+++ b/backends/AnalyseAsm.hs
@@ -186,8 +186,8 @@ addCalls unknownSize
               return $ localStack + maximum (0 : calledStacks)
 
 -- | Analyse assembler and return C source defining sizes.
-analyseAsm :: String -> PassM String
-analyseAsm asm
+analyseAsm :: Maybe [String] -> String -> PassM String
+analyseAsm mprocs asm
   =  do let stream = parseAsm asm
         veryDebug $ pshow stream
         cs <- getCompState
@@ -196,7 +196,11 @@ analyseAsm asm
         debug $ concat [printf "  %-40s %5d %5d %s\n"
                           func (fiStack fi) (fiTotalStack fi)
                           (concat $ intersperse " " $ Set.toList $ fiCalls fi)
-                        | (func, fi) <- Map.toList info]
+                        | (func, fi) <- Map.toList $ filterNames info]
         let lines = ["const int " ++ func ++ "_stack_size = " ++ show (fiTotalStack fi) ++ ";\n"
-                     | (func, fi) <- Map.toList info]
+                     | (func, fi) <- Map.toList $ filterNames info]
         return $ concat lines
+  where
+    filterNames = case mprocs of
+      Nothing -> id
+      Just m -> (`Map.intersection` (Map.fromList (zip m (repeat ()))))
diff --git a/backends/GenerateC.hs b/backends/GenerateC.hs
index ff2fcdb..8f3e588 100644
--- a/backends/GenerateC.hs
+++ b/backends/GenerateC.hs
@@ -34,6 +34,7 @@ module GenerateC
   , genName
   , genRightB
   , genStatic
+  , needStackSizes
   , justOnly
   , withIf
   ) where
@@ -159,6 +160,20 @@ cgenOps = GenOps {
 generateC :: (Handle, Handle) -> String -> A.AST -> PassM ()
 generateC = generate cgenOps
 
+needStackSizes :: (CSMR m, Die m) => m [A.Name]
+needStackSizes
+  = do cs <- getCompState
+       main <- if csHasMain cs
+                  then tlpInterface >>* fst >>* singleton
+                  else return []
+       return $ nub $ (Set.toList $ csParProcs cs `Set.difference`
+                                      Set.fromList (map (A.Name emptyMeta . fst) (csExternals cs)))
+                ++ [A.Name emptyMeta n
+                   | A.NameDef {A.ndName = n
+                               ,A.ndSpecType=A.Proc _ (_,A.Recursive) _ _
+                               } <- Map.elems $ csNames cs]
+                ++ main
+
 cgenTopLevel :: String -> A.AST -> CGen ()
 cgenTopLevel headerName s
     =  do tell ["#define occam_INT_size ", show cIntSize,"\n"]
@@ -180,13 +195,9 @@ cgenTopLevel headerName s
           sequence_ [tell ["#include \"", usedFile, ".tock.h\"\n"]
                     | usedFile <- Set.toList $ csUsedFiles cs]
 
+          nss <- needStackSizes
           sequence_ [tell ["extern int "] >> genName n >> tell ["_stack_size;\n"]
-                     | n <- (Set.toList $ csParProcs cs `Set.difference`
-                                         Set.fromList (map (A.Name emptyMeta . fst) (csExternals cs)))
-                           ++ [A.Name emptyMeta n | A.NameDef
-                                    {A.ndName = n
-                                    ,A.ndSpecType=A.Proc _ (_,A.Recursive) _ _
-                                    } <- Map.elems $ csNames cs]]
+                     | n <- nss]
 
           when (csHasMain cs) $ do
             (tlpName, tlpChans) <- tlpInterface