sed, insert file before last line

[T o n g <mlist4suntong@yahoo.com>]

Hi, 

The following inserting file method for sed used to be working, even 
before last line, but not any more. Is it a bug in the current sed?

Demo of inserting file method with sed:

mkdir /tmp/test
printf '%s\n' {1..3} > /tmp/test/f1
printf '%s\n' {one,two,three,four,five,six,seven,eight,nine,ten} > /tmp/
test/f2

$ cat /tmp/test/f2 | sed -e "/nine/r /tmp/test/f1" -e //N
one
two
three
four
five
six
seven
eight
1
2
3
nine
ten

$ cat /tmp/test/f2 | sed -e "/ten/r /tmp/test/f1" -e //N
one
two
three
four
five
six
seven
eight
nine
ten
1
2
3

$ sed --version
GNU sed version 4.2.1
... 

I.e., the inserting file before the line method works everywhere except 
the last line. It used to be working before. I didn't record the previous 
working version, neither I recorded the time I test it. But I do dig the 
above from my old note, which I'm sure had been working before.

Is it a bug in the current sed?

Thanks