MetronomeMark alignment after break

[Daniel Rosen]

In the example below, "Tempo II" is aligned differently from "Tempo I," and the 
only difference between the two that I can see is that there's a full measure 
rest in the top staff immediately after "Tempo II" occurs. How can I get "Tempo 
II" to align the same as "Tempo I?" I've tried playing around with 
MetronomeMark #'break-align-symbols to no avail; could this be a bug?

\version "2.16.1"

<<
  \new Staff {
    c''1
    c''1
    R1
  }
  \new Staff {
    c''4 c'' c'' c'' \break \tempo "Tempo I"
    c''4 c'' c'' c'' \break \tempo "Tempo II"
    c''4 c'' c'' c''
  }
>>

DR