Scalar product in objective

I’ll illustrate the problem with the following simple example:

import JuMP
l = ones(4)
model= JuMP.Model()
JuMP.@variable(model, x)
JuMP.@variable(model, y1)
JuMP.@variable(model, y2)
epxr = [
    JuMP.@expression(model, y1 - 1), 
    JuMP.@expression(model, y2 - 2)]

In my objective function I want to have the scalar product of l and expr.
This does not work:

JuMP.@objective(model, Min,  x * 3 + l[2:3]' * epxr))

MethodError: no method matching add_to_expression!(::GenericAffExpr{Float64,VariableRef}, ::Adjoint{Float64,Array{Float64,1}}, ::Array{GenericAffExpr{Float64,VariableRef},1})

FYI: If you would remove the term x * 3 it would work.

This does work:

JuMP.@objective(model, Min, x * 3 + sum(l[2:3] .* epxr))

This does too:

exp2 = l[2:3]' * epxr
JuMP.@objective(model, Min, x * 3 + exp2)


That looks like a bug. Please open an issue at JuMP.jl.