diff --git a/fasta.cabal b/fasta.cabal
--- a/fasta.cabal
+++ b/fasta.cabal
@@ -10,7 +10,7 @@
 -- PVP summary:      +-+------- breaking API changes
 --                   | | +----- non-breaking API additions
 --                   | | | +--- code changes with no API change
-version:             0.6.2.0
+version:             0.7.0.0
 
 -- A short (one-line) description of the package.
 synopsis:            A simple, mindless parser for fasta files.
diff --git a/src/Data/Fasta/ByteString/Lazy/Parse.hs b/src/Data/Fasta/ByteString/Lazy/Parse.hs
--- a/src/Data/Fasta/ByteString/Lazy/Parse.hs
+++ b/src/Data/Fasta/ByteString/Lazy/Parse.hs
@@ -49,9 +49,7 @@
     header <- manyTill (satisfy (/= '>')) eol
     fseq <- manyTill anyChar eoe
     return (FastaSequence { fastaHeader = B.pack header
-                          , fastaSeq = B.pack
-                                     . map toUpper
-                                     . removeWhitespace $ fseq } )
+                          , fastaSeq    = B.pack . removeWhitespace $ fseq } )
   where
     removeWhitespace = filter (`notElem` ("\n\r " :: String))
 
diff --git a/src/Data/Fasta/ByteString/Parse.hs b/src/Data/Fasta/ByteString/Parse.hs
--- a/src/Data/Fasta/ByteString/Parse.hs
+++ b/src/Data/Fasta/ByteString/Parse.hs
@@ -46,10 +46,7 @@
     header <- manyTill (satisfy (/= '>')) eol
     fseq <- manyTill anyChar eoe
     return (FastaSequence { fastaHeader = B.pack header
-                          , fastaSeq = B.pack
-                                     . map toUpper
-                                     . removeWhitespace
-                                     $ fseq } )
+                          , fastaSeq = B.pack . removeWhitespace $ fseq } )
   where
     removeWhitespace = filter (`notElem` ("\n\r " :: String))
 
diff --git a/src/Data/Fasta/String/Parse.hs b/src/Data/Fasta/String/Parse.hs
--- a/src/Data/Fasta/String/Parse.hs
+++ b/src/Data/Fasta/String/Parse.hs
@@ -42,8 +42,7 @@
     header <- manyTill (satisfy (/= '>')) eol
     fseq <- manyTill anyChar eoe
     return ( FastaSequence { fastaHeader = header
-                           , fastaSeq    = map toUpper
-                                         $ removeWhitespace fseq } )
+                           , fastaSeq    = removeWhitespace fseq } )
   where
     removeWhitespace = filter (`notElem` "\n\r ")
 
diff --git a/src/Data/Fasta/Text/Lazy/Parse.hs b/src/Data/Fasta/Text/Lazy/Parse.hs
--- a/src/Data/Fasta/Text/Lazy/Parse.hs
+++ b/src/Data/Fasta/Text/Lazy/Parse.hs
@@ -49,9 +49,7 @@
     header <- manyTill (satisfy (/= '>')) eol
     fseq <- manyTill anyChar eoe
     return (FastaSequence { fastaHeader = T.pack header
-                          , fastaSeq = T.pack
-                                     . map toUpper
-                                     . removeWhitespace $ fseq } )
+                          , fastaSeq = T.pack . removeWhitespace $ fseq } )
   where
     removeWhitespace = filter (`notElem` ("\n\r " :: String))
 
diff --git a/src/Data/Fasta/Text/Parse.hs b/src/Data/Fasta/Text/Parse.hs
--- a/src/Data/Fasta/Text/Parse.hs
+++ b/src/Data/Fasta/Text/Parse.hs
@@ -46,10 +46,7 @@
     header <- manyTill (satisfy (/= '>')) eol
     fseq <- manyTill anyChar eoe
     return (FastaSequence { fastaHeader = T.pack header
-                          , fastaSeq = T.pack
-                                     . map toUpper
-                                     . removeWhitespace
-                                     $ fseq } )
+                          , fastaSeq = T.pack . removeWhitespace $ fseq } )
   where
     removeWhitespace = filter (`notElem` ("\n\r " :: String))