fwrite crashes RStudio when na argument is passed

[contefranz]

I am using R v. 3.3.0 and RStudio 0.99.1197. The session crashes when the argument na is passed to fwrite(). Here is the minimal:

dt = data.table( a = 1:10, b = letters[ 1:10 ] )

# working with message:
# Your platform/environment has not detected OpenMP support. 
# fwrite() will still work, but slower in single threaded mode.
fwrite( dt, '~/Desktop/test.csv' )

# NOT WORKING 
fwrite( dt, '~/Desktop/test.csv', na = NA )

Is there anyone who's experiencing this?
Thanks in advance

[arunsrinivasan]

The argument needs to be a string. na = "NA" works. We need to make sure to convert to string before calling the C-function.