Warm Starts in JuMP 0.21 & GLPK 0.12.1

When I run a version of the code below, I receive the following error:

Warning: MathOptInterface.VariablePrimalStart() is not supported by MathOptInterface.Bridges.LazyBridgeOptimizer{GLPK.Optimizer}. This information will be discarded.

ā”” @ MathOptInterface.Utilities ~/.julia/packages/MathOptInterface/XiH8D/src/Utilities/copy.jl:140

using JuMP
using GLPK

    prev_u = .15
	model = Model(with_optimizer_attributes(GLPK.Optimizer))
	@variable(model, u >= 0.1, start = prev_u)

What am I doing incorrectly?

GLPK does not support starting values. Neither does Clp. Cbc does though.