diff --git a/CHANGELOG.markdown b/CHANGELOG.markdown
--- a/CHANGELOG.markdown
+++ b/CHANGELOG.markdown
@@ -1,3 +1,7 @@
+0.1.1.0
+
+Add ExportError exception
+
 0.1.0.1
 
-Added MatrixMarket module from `accelerate-examples` SMVM
+Add MatrixMarket module from `accelerate-examples` SMVM
diff --git a/matrix-market-attoparsec.cabal b/matrix-market-attoparsec.cabal
--- a/matrix-market-attoparsec.cabal
+++ b/matrix-market-attoparsec.cabal
@@ -1,5 +1,5 @@
 name:                matrix-market-attoparsec
-version:             0.1.0.9
+version:             0.1.1.0
 synopsis:            Parsing and serialization functions for the NIST Matrix Market format
 description:         Parsing and serialization functions for the NIST Matrix Market format.
 homepage:            https://github.com/ocramz/matrix-market-attoparsec
diff --git a/src/Control/Exception/Common.hs b/src/Control/Exception/Common.hs
--- a/src/Control/Exception/Common.hs
+++ b/src/Control/Exception/Common.hs
@@ -1,4 +1,5 @@
 {-# language DeriveDataTypeable #-}
+{-# language LambdaCase #-}
 module Control.Exception.Common where
 
 import Control.Exception
@@ -8,5 +9,12 @@
 
 data ImportError = FileParseError String String deriving (Eq, Typeable)
 instance Show ImportError where
-  show (FileParseError s s2) = unwords [s, ": File parse error:", s2]
+  show = \case
+    FileParseError s s2 -> unwords [s, ": File parse error:", s2]
 instance Exception ImportError
+
+data ExportError = FormatExportNotSupported String String deriving (Eq, Typeable)
+instance Show ExportError where
+  show = \case
+    FormatExportNotSupported s sty -> unwords [s, ":", sty, "format not supported"]
+instance Exception ExportError
diff --git a/src/Data/Matrix/MatrixMarket.hs b/src/Data/Matrix/MatrixMarket.hs
--- a/src/Data/Matrix/MatrixMarket.hs
+++ b/src/Data/Matrix/MatrixMarket.hs
@@ -17,9 +17,9 @@
 -----------------------------------------------------------------------------
 module Data.Matrix.MatrixMarket
        (-- * Load
-        readMatrix, readArray,
+        readMatrix, readMatrix', readArray,
         -- * Save
-        writeMatrix, writeArray,
+        writeMatrix, writeMatrix', writeArray,
         -- 
         Matrix(..), Array(..),
         Format (Coordinate, Array), Structure (General, Symmetric, Hermitian, Skew),
@@ -29,6 +29,6 @@
         -- ** Array-related
         dimArr, numDatArr,
         -- * Exceptions
-        ImportError) where
+        ImportError(..)) where
 
 import Data.Matrix.MatrixMarket.Internal as M
diff --git a/src/Data/Matrix/MatrixMarket/Internal.hs b/src/Data/Matrix/MatrixMarket/Internal.hs
--- a/src/Data/Matrix/MatrixMarket/Internal.hs
+++ b/src/Data/Matrix/MatrixMarket/Internal.hs
@@ -23,7 +23,7 @@
         Format (Coordinate, Array), Structure (General, Symmetric, Hermitian, Skew),
         nnz, dim, numDat,
         dimArr, numDatArr,
-        ImportError) where
+        ImportError(..)) where
 
 
 
@@ -40,7 +40,7 @@
 import qualified Data.ByteString.Lazy           as L
 
 import Control.Monad.Catch
-import Control.Exception.Common
+import Control.Exception.Common (ImportError(..), ExportError(..))
 
 
 
@@ -187,7 +187,7 @@
 readMatrix :: FilePath -> IO (Matrix S.Scientific)
 readMatrix file = L.readFile file >>= readMatrix'
 
--- | Load a matrix (sparse, i.e. in Coordinate format) from a bytestring.
+-- | Load a matrix (sparse, i.e. in Coordinate format) from a lazy 'L.Bytestring'.
 readMatrix' :: L.ByteString -> IO (Matrix S.Scientific)
 readMatrix' chunks =
   case L.parse matrix chunks of
@@ -238,18 +238,20 @@
 
 -- | Serialize a sparse matrix in Coordinate format
 writeMatrix :: Show b => FilePath -> Matrix b -> IO ()
-writeMatrix file = L.writeFile file . writeMatrix'
+writeMatrix fp mat = do
+  mbs <- writeMatrix' mat
+  L.writeFile fp mbs
 
 -- | Serialize a sparse matrix in Coordinate format as a bytestring
-writeMatrix' :: Show b => Matrix b -> L.ByteString
+writeMatrix' :: (MonadThrow m, Show b) => Matrix b -> m L.ByteString
 writeMatrix' mat =
   case mat of (RMatrix d nz s dat) ->
-                matrixByteString d nz R s dat
+                pure $ matrixByteString d nz R s dat
               (CMatrix d nz s dat) ->
-                matrixByteString d nz C s dat
+                pure $ matrixByteString d nz C s dat
               (IntMatrix d nz s dat) ->
-                matrixByteString d nz I s dat
-              _ -> error "writeMatrix : PatternMatrix not implemented yet"
+                pure $ matrixByteString d nz I s dat
+              _ -> throwM (FormatExportNotSupported "writeMatrix" "PatternMatrix not implemented yet")
      where
        matrixByteString di nz t s d =
          L.concat [headerStr Coordinate t s,
@@ -282,7 +284,6 @@
 
 
 
--- | helpers
 
 -- | Number of matrix nonzeros
 nnz :: Matrix t -> Int