odd "create master" behavior

I'm trying to create a master list.

    $ echo 'bob mike janus' > wl.txt
    $ aspell --lang=en create master ./dict.cwl < wl.txt
    Warning: The word "bob mike janus" is invalid. The character ' ' (U+20) 
    may not appear in the middle of a word. Skipping word.
    Segmentation fault

If I edit the file and separate each word by a carriage return, I get:

    $ aspell --lang=en create master ./dict.cwl < wl.txt
    $ aspell dump master ./dict.cwl
    bo
    mik
    janu

TIA, gsf