  We find that the recently-proposed ghost-free interaction of a 2-form gauge
field in four dimensions, which contains derivative couplings in a
nonperturbative manner, can be regarded as a resummation of ghostly interaction
terms. We investigate the higher derivative structure of this model in a
minisuperspace description and demonstrate that the higher derivative terms can
be removed by taking appropriate combinations of the Euler-Lagrange equations,
while a truncation at a finite order spoils this structure. We also show that
this nature is peculiar to four dimensions.
