diff --git a/README.md b/README.md
index 74ececb..3e80431 100644
--- a/README.md
+++ b/README.md
@@ -118,7 +118,7 @@ save(Stream(format"CSV", io), it)
 
 The ``save`` function takes a number of arguments:
 ````julia
-save(f::FileIO.File{FileIO.format"CSV"}, data; delim=',', quotechar='"', escapechar='"', nastring="NA", header=true)
+save(f::FileIO.File{FileIO.format"CSV"}, data; delim=',', quotechar='"', escapechar='"', nastring="", header=true)
 ````
 
 #### Arguments
diff --git a/src/csv_writer.jl b/src/csv_writer.jl
index c439490..09b06ff 100644
--- a/src/csv_writer.jl
+++ b/src/csv_writer.jl
@@ -45,7 +45,7 @@ end
     end
 end
 
-function _save(io, data; delim=',', quotechar='"', escapechar='"', nastring="NA", header=true)
+function _save(io, data; delim=',', quotechar='"', escapechar='"', nastring="", header=true)
     isiterabletable(data) || error("Can't write this data to a CSV file.")
 
     it = getiterator(data)
@@ -62,7 +62,7 @@ function _save(io, data; delim=',', quotechar='"', escapechar='"', nastring="NA"
     _writecsv(io, it, eltype(it), delim, quotechar, escapechar, nastring)
 end
 
-function _save(filename::AbstractString, data; delim=',', quotechar='"', escapechar='"', nastring="NA", header=true)
+function _save(filename::AbstractString, data; delim=',', quotechar='"', escapechar='"', nastring="", header=true)
     isiterabletable(data) || error("Can't write this data to a CSV file.")
 
     ext = last(split(filename, '.'))
@@ -80,19 +80,19 @@ end
 
 
 
-function fileio_save(f::FileIO.File{FileIO.format"CSV"}, data; delim=',', quotechar='"', escapechar='"', nastring="NA", header=true)
+function fileio_save(f::FileIO.File{FileIO.format"CSV"}, data; delim=',', quotechar='"', escapechar='"', nastring="", header=true)
     return _save(f.filename, data, delim=delim, quotechar=quotechar, escapechar=escapechar, nastring=nastring, header=header)
 end
 
-function fileio_save(f::FileIO.File{FileIO.format"TSV"}, data; delim='\t', quotechar='"', escapechar='"', nastring="NA", header=true)
+function fileio_save(f::FileIO.File{FileIO.format"TSV"}, data; delim='\t', quotechar='"', escapechar='"', nastring="", header=true)
     return _save(f.filename, data, delim=delim, quotechar=quotechar, escapechar=escapechar, nastring=nastring, header=header)
 end
 
-function fileio_save(s::FileIO.Stream{FileIO.format"CSV"}, data; delim=',', quotechar='"', escapechar='"', nastring="NA", header=true)
+function fileio_save(s::FileIO.Stream{FileIO.format"CSV"}, data; delim=',', quotechar='"', escapechar='"', nastring="", header=true)
     return _save(s.io, data, delim=delim, quotechar=quotechar, escapechar=escapechar, nastring=nastring, header=header)
 end
 
-function fileio_save(s::FileIO.Stream{FileIO.format"TSV"}, data; delim='\t', quotechar='"', escapechar='"', nastring="NA", header=true)
+function fileio_save(s::FileIO.Stream{FileIO.format"TSV"}, data; delim='\t', quotechar='"', escapechar='"', nastring="", header=true)
     return _save(s.io, data, delim=delim, quotechar=quotechar, escapechar=escapechar, nastring=nastring, header=header)
 end
 
@@ -113,7 +113,7 @@ mutable struct CSVFileSaveStream{T}
     header::Bool
 end
                             
-function fileio_savestreaming(f::FileIO.File{T}, data=nothing; delim=_delim(T), quotechar='"', escapechar='"', nastring="NA", 
+function fileio_savestreaming(f::FileIO.File{T}, data=nothing; delim=_delim(T), quotechar='"', escapechar='"', nastring="", 
                               header=true) where T <: CSV_or_TSV
     io = open(f.filename, "w")
 
@@ -124,7 +124,7 @@ function fileio_savestreaming(f::FileIO.File{T}, data=nothing; delim=_delim(T),
     return CSVFileSaveStream(io, data!==nothing, delim, quotechar, escapechar, nastring, header)
 end
 
-function fileio_savestreaming(s::FileIO.Stream{T}, data=nothing; delim=_delim(T), quotechar='"', escapechar='"', nastring="NA", 
+function fileio_savestreaming(s::FileIO.Stream{T}, data=nothing; delim=_delim(T), quotechar='"', escapechar='"', nastring="", 
                               header=false) where T <: CSV_or_TSV
 
     if data!==nothing