We have searched for the decay B-->D-s1(+)(2536)X and measured an uppe
r limit for the inclusive branching fraction of B(B-->(D) over bar(s1)
(+)X)<0.96% at the 90% confidence level. This limit is small compared
with the total expected B-->(D) over bar()D(*)KX rate. Assuming facto
rization, the D-s1(+) decay constant is constrained to be f(Dsl+)<114
MeV at the 90% confidence level, at least 2.5 times smaller than that
of D-s(+). [S0556-2821(98)01809-8].