Unable to multiply two triangular sparse matrices

[KlausC]

Multiplying two UpperTriangular{SparseMatrixCSC} and friends should return a matrix of the same type.
Computational effort should be approximately 1/4 of sparse multiplication of SparseMatrixCSC.

It throws a Method Error instead.

julia> X = UpperTriangular(sprand(100, 100, 10*1e-2));

julia> X * X
ERROR: MethodError: no method matching lmul!(::UpperTriangular{Float64,SparseMatrixCSC{Float64,Int64}}, ::SparseMatrixCSC{Float64,Int64})
  ...
Stacktrace:
 [1] *(::UpperTriangular{Float64,SparseMatrixCSC{Float64,Int64}}, ::UpperTriangular{Float64,SparseMatrixCSC{Float64,Int64}}) at /home/crusius/julia-1.0.5/share/julia/stdlib/v1.0/LinearAlgebra/src/triangular.jl:1627