diff --git a/tower-aadl/src/Tower/AADL.hs b/tower-aadl/src/Tower/AADL.hs
index 8584e79..3cd31dd 100644
--- a/tower-aadl/src/Tower/AADL.hs
+++ b/tower-aadl/src/Tower/AADL.hs
@@ -26,9 +26,11 @@ import           Data.Char
 import           Control.Monad hiding (forever)
 
 import           System.FilePath (addExtension, takeFileName, (<.>))
+import           System.IO (hPutStrLn, stderr)
 import           System.Exit (exitFailure)
-
+import           MonadLib (runWriterT)
 import           Text.PrettyPrint.Leijen hiding ((</>))
+import qualified Text.PrettyPrint
 
 import qualified Ivory.Compile.C.CmdlineFrontend as O
 import qualified Ivory.Compile.C.Types as O
@@ -108,7 +110,12 @@ compileTowerAADLForPlatform fromEnv mkEnv twr' = do
 
   unless (validCIdent appname) $ error $ "appname must be valid c identifier; '"
                                         ++ appname ++ "' is not"
-  cmodules <- O.compileUnits mods copts
+  (cmodules, errors) <- runWriterT $ O.compileUnits mods copts
+  hPutStrLn stderr
+    . Text.PrettyPrint.render
+    $ Text.PrettyPrint.vcat
+        errors
+
   let (appMods, libMods) =
         partition (\m -> O.unitName m `elem` pkgs) cmodules
   O.outputCompiler appMods (as osspecific) (osSpecificOptsApps osspecific cfg copts)
diff --git a/tower-aadl/tower-aadl.cabal b/tower-aadl/tower-aadl.cabal
index fc6bfa0..29787e5 100644
--- a/tower-aadl/tower-aadl.cabal
+++ b/tower-aadl/tower-aadl.cabal
@@ -29,6 +29,8 @@ library
                , containers
                , directory
                , filepath
+               , monadLib >= 3.7
+               , pretty >= 1.1
                , wl-pprint
                , ivory >= 0.1.0.2
                , ivory-artifact
diff --git a/tower-mini/src/Tower/Mini.hs b/tower-mini/src/Tower/Mini.hs
index a872511..8857bd4 100644
--- a/tower-mini/src/Tower/Mini.hs
+++ b/tower-mini/src/Tower/Mini.hs
@@ -42,7 +42,9 @@ import Data.List                 (partition)
 import MonadLib                  (forM_, runWriterT, when)
 import System.FilePath           ((</>))
 import System.Exit               (exitFailure)
+import System.IO (hPutStrLn, stderr)
 import Text.PrettyPrint.Mainland ((<+>), putDoc, text)
+import Text.PrettyPrint (render, vcat)
 
 import qualified Data.Map as Map
 
@@ -241,7 +243,8 @@ compileTowerMini _fromEnv mkEnv comps = do
                             , outHdrDir = Just (f </> name </> "include")
                             , outArtDir = Just (f </> name)
                             }
-    cmodules <- compileUnits mods copts'
+    (cmodules, errors) <- runWriterT $ compileUnits mods copts'
+    hPutStrLn stderr $ render $ vcat errors
 
     let (appMods, libMods) =
           partition (\m -> unitName m `elem` packages) cmodules
diff --git a/tower-mini/tower-mini.cabal b/tower-mini/tower-mini.cabal
index 6d86d47..222a9a8 100644
--- a/tower-mini/tower-mini.cabal
+++ b/tower-mini/tower-mini.cabal
@@ -16,6 +16,7 @@ library
                , filepath
                , mainland-pretty >= 0.4.0.0
                , monadLib
+               , pretty >= 1.1
                , ivory >= 0.1.0.2
                , ivory-backend-c
                , tower