Dynamic mark at the end of a bar

[David Sumbler]

I often use 's1*0\!' to end a hairpin just before a barline.

But how can a get a dynamic mark (e.g. 'ff') to appear at the end of a
bar?  In the following example, the first hairpin behaves as I want.
The second one ends with a dynamic, but the new dynamic appears at the
start of the following bar, even though it is attached to an item which
occurs on the barline.

\version "2.18.0"

{
    c''4\< c''2. s1*0\! |
    R1 |
    c''4\< c''2. s1*0\ff |
    R1 |
}

David