field enhancer of type "Single nested property" on body fields break POST and PATCH

It seems like when using the field enhancer of type "Single nested property" on body fields I cannot POST and PATCH via JSONAPI.
I am using the enhancer on the body field with path "processed". When using GET the enhancer works nicely giving me:

body:"bla"

instead of

body: {
  value:"bla",
  format":"plain_text",
  processed:"bla",
  summary:null
}

However when I try to POST or PATCH with the field enhancer turned on it doesn't seem to accept the input. I tried posting the body text using both formats. I would think that posting in the "Single nested property" form would not make sense in this case, since the processed field is computed.