diff --git a/sequence-formats.cabal b/sequence-formats.cabal
--- a/sequence-formats.cabal
+++ b/sequence-formats.cabal
@@ -1,6 +1,6 @@
 cabal-version:      >=1.10
 name:               sequence-formats
-version:            1.6.0
+version:            1.6.1
 license:            GPL-3
 license-file:       LICENSE
 maintainer:         stephan.schiffels@mac.com
diff --git a/src/SequenceFormats/Plink.hs b/src/SequenceFormats/Plink.hs
--- a/src/SequenceFormats/Plink.hs
+++ b/src/SequenceFormats/Plink.hs
@@ -164,9 +164,9 @@
     genoLineToBytes genoLine = go (toList genoLine)
       where
         go :: [GenoEntry] -> [Word8]
-        go (g1 : g2 : g3 : g4 : rest) = constructByte [g1, g2, g3, g4] : go rest
-        -- go (g1 : g2 : g3 : g4 : rest) = constructByte [g4, g3, g2, g1] : go rest
-        go genoEntries = [constructByte genoEntries]
+        go [] = [] -- empty list for recursion stop
+        go (g1 : g2 : g3 : g4 : rest) = constructByte [g1, g2, g3, g4] : go rest -- at least 5 entries -> more than 1 byte
+        go genoEntries = [constructByte genoEntries] -- four or less entries -> 1 byte
         constructByte :: [GenoEntry] -> Word8
         constructByte [] = error "constructByte - should never happen"
         constructByte [g] = genoEntryToByte g