Comment 5 for bug 1535427

Follow your suggestion i wrapped the text inside the body on p tags. The error still persist. I tried the same operation on a windows7 machine running calibre 2.49 x64 and the merge works.
This is the error that the merge operation raise on my Linux machine.
calibre, version 2.49.0.r74.g78fcc5c
ERROR: Unhandled exception: <b>AbortError</b>:The master file (&page1.html) must be one of the files being merged

calibre 2.49.0.r74.g78fcc5c isfrozen: False is64bit: True
Linux-4.4.0-mainline-x86_64-with-glibc2.2.5 Linux ('64bit', '')
('Linux', '4.4.0-mainline', '#1 SMP PREEMPT Mon Jan 11 15:37:58 CET 2016')
Python 2.7.11
Linux: ('', '', '')
Successfully initialized third party plugins: DeDRM
Traceback (most recent call last):
  File "/usr/lib/calibre/calibre/gui2/tweak_book/boss.py", line 66, in ans
    return func(*args, **kwargs)
  File "/usr/lib/calibre/calibre/gui2/tweak_book/boss.py", line 1161, in merge_requested
    merge(current_container(), category, names, master)
  File "/usr/lib/calibre/calibre/ebooks/oeb/polish/split.py", line 480, in merge
    raise AbortError('The master file (%s) must be one of the files being merged' % master)
AbortError: The master file (&page1.html) must be one of the files being merged