  We determine a basis of dimension-7 operators which arise at O($a$) in the
Symanzik expansion of the $\Delta B=2$ operators with static heavy quarks. We
consider both Wilson-like and Ginsparg-Wilson light quarks. Exact chiral
symmetry reduces the number of these O($a$) counterterms by a factor of two.
Only a subset of these operators has previously appeared in the literature. We
then extend the analysis to the O($1/m$) operators contributing beyond the
static approximation.
