diff --git a/ChangeLog.md b/ChangeLog.md
--- a/ChangeLog.md
+++ b/ChangeLog.md
@@ -2,6 +2,10 @@
 
 ## [Unreleased]
 
+## [0.1.2.1] - 2019-12-9
+### Changed
+- changed `forbidden` parameter type
+
 ## [0.1.2.0] - 2019-12-5
 ### Added
 - wrike-426952824 : added Ecoli and CHO codon tables
diff --git a/cobot-tools.cabal b/cobot-tools.cabal
--- a/cobot-tools.cabal
+++ b/cobot-tools.cabal
@@ -4,10 +4,10 @@
 --
 -- see: https://github.com/sol/hpack
 --
--- hash: ea5b0488b2bf324cf7921fa277e07d923d6a1eee5bb0f9e6a940db2753897610
+-- hash: f2ccf441623f2e23d11376c3e75ce4d4f1cdd056329f2470c7113e541c1dddcb
 
 name:           cobot-tools
-version:        0.1.2.0
+version:        0.1.2.1
 synopsis:       Biological data file formats and IO
 description:    Please see the README on GitHub at <https://github.com/less-wrong/cobot-tools#readme>
 category:       Bio
diff --git a/src/Bio/Tools/Sequence/CodonOptimization/Types.hs b/src/Bio/Tools/Sequence/CodonOptimization/Types.hs
--- a/src/Bio/Tools/Sequence/CodonOptimization/Types.hs
+++ b/src/Bio/Tools/Sequence/CodonOptimization/Types.hs
@@ -5,7 +5,6 @@
     , defaultForbiddenRegexp
     ) where
 
-import qualified Data.ByteString.Lazy as BSL (ByteString)
 import           Data.Default                (Default (..))
 import           GHC.Generics                (Generic)
 
@@ -30,14 +29,14 @@
         , rnaFoldingWindow   :: Int                -- ^ length of the window for RNA folding score calculation (bp)
         , forbiddenDNAWeight :: Double             -- ^ forbidden DNA motifs score weight
         , gcContentDesired   :: Int                -- ^ desired gc content in percents
-        , forbiddenSequence  :: [BSL.ByteString]   -- ^ list of forbidden patterns
+        , forbiddenSequence  :: [String]           -- ^ list of forbidden patterns
         }
     deriving (Eq, Show, Generic)
 
 instance Default CodonScoreConfig where
   def = CodonScoreConfig CHO 3 1 1 0.5 1.4 40 0.001 2.6 100 1 43 defaultForbiddenRegexp
 
-defaultForbiddenRegexp :: [BSL.ByteString]
+defaultForbiddenRegexp :: [String]
 defaultForbiddenRegexp =
     [ "ATTTA"
     , "ATACTCCCCC"