diff --git a/changelog b/changelog
--- a/changelog
+++ b/changelog
@@ -1,5 +1,8 @@
 -*-change-log-*-
 
+0.7.4	Nov 2014
+	* Ignore non-printable characters for compatibility with Maca
+
 0.7.0	Nov 2013
 	* Output guessing results for unknown words 
 	* Allow "--noana" option in the client/server mode
diff --git a/concraft-pl.cabal b/concraft-pl.cabal
--- a/concraft-pl.cabal
+++ b/concraft-pl.cabal
@@ -1,5 +1,5 @@
 name:               concraft-pl
-version:            0.7.3
+version:            0.7.4
 synopsis:           Morphological tagger for Polish
 description:
     A morphological tagger for Polish based on the concraft library.
@@ -28,12 +28,12 @@
       , sgd                     >= 0.3.3    && < 0.4
       , containers              >= 0.4      && < 0.6
       , bytestring              >= 0.9      && < 0.11
-      , text                    >= 0.11     && < 1.2
-      , aeson                   >= 0.6      && < 0.8
+      , text                    >= 0.11     && < 1.3
+      , aeson                   >= 0.6      && < 0.9
       , binary                  >= 0.5      && < 0.8
       , process                 >= 1.1      && < 1.3
-      , mtl                     >= 2.0      && < 2.2
-      , transformers            >= 0.2      && < 0.4
+      , mtl                     >= 2.0      && < 2.3
+      , transformers            >= 0.2      && < 0.5
       , network                 >= 2.3      && < 2.7
       , lazy-io                 >= 0.1      && < 0.2
       , split                   >= 0.2      && < 0.3
diff --git a/src/NLP/Concraft/Polish/Maca.hs b/src/NLP/Concraft/Polish/Maca.hs
--- a/src/NLP/Concraft/Polish/Maca.hs
+++ b/src/NLP/Concraft/Polish/Maca.hs
@@ -213,29 +213,33 @@
 putMaca x (MacaPool c) = writeChan c x
 
 
--- | Analyse paragraph with Maca.
--- The function is thread-safe.
+-- | Analyse paragraph with Maca.  The function is thread-safe.  As a
+-- pre-processing step, all non-printable characters are removed from
+-- the input (based on empirical observations, Maca behaves likewise).
 macaPar :: MacaPool -> T.Text -> IO [Sent Tag]
-macaPar pool par = do
+macaPar pool par0 = do
+    let par = T.filter C.isPrint par0
     maca <- popMaca pool
     doMacaPar maca par `finally` putMaca maca pool
 
 
-----------------------------
--- Weight
-----------------------------
+------------------------------------------------------------
+-- Weight: a number of non-space characters
+------------------------------------------------------------
 
 
--- | A number of non-space characters in a text.
+-- | A weight of a text.
 textWeight :: T.Text -> Int
+-- textWeight = T.length . T.filter C.isAlphaNum
 textWeight = T.length . T.filter (not . C.isSpace)
+-- textWeight = T.length . T.filter ((&&) <$> not . C.isSpace <*> C.isPrint)
 
 
--- | A number of non-space characters in a sentence.
+-- | A weight of a segment.
 segWeight :: Seg t -> Int
 segWeight = textWeight . orth . word
 
 
--- | A number of non-space characters in a sentence.
+-- | A weight of a sentence.
 sentWeight :: Sent t -> Int
 sentWeight = sum . map segWeight