Merge files and the doctype declaration gets omitted from the merged document, whilst being present in both original xhtml files.
visually, this
Code:
<?xml version="1.0" encoding="utf-8"?>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.1//EN"
"http://www.w3.org/TR/xhtml11/DTD/xhtml11.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
after merging becomes
Code:
<?xml version="1.0" encoding="utf-8"?>
<html xmlns="http://www.w3.org/1999/xhtml">
adding obviousness, we're talking epub2 here.
edit: i'm using the OSX build on El Capitan (v 10.11.1)
(is this the right venue for Sigil bug reports?)