Duplicate .html in filenames

Using 1.58.1 XSL stylesheets, the filenames for my
files where I specify a filename using the DBHTML PI
have an additional .html extension.

My DBHTML's look like:
<?dbhtml filename="Hlp_C_ESSOLV.html"?>

The filename is:
Hlp_C_ESSOLV.html.html

Prior versions of the stylesheets did not have this problem