file extensions are purely decorative for these files - crt and cer are both common extensions used on windows, but the file formats predate the existence of windows (or dos, for that matter)
crt is a common extension for a PEM encoded file for use with apache though, to distinguish from the .key file; It is the only ascii encoding for certificates. For that reason, I expect the above procedure to work, as you are expecting a ascii encoded file ending in .crt and this will give you an ascii encoded file ending in crt :)
