Can't add title to 2D function plot

[RossBoylan]

Problem

plot((x, y)->x+y/2.0, 0.1, 5, -1, 3, Guide.Title("My Title"))

yields this error:

ERROR: Layers can't be used with elements of type Gadfly.Guide.Title
Stacktrace:
  [1] error(s::String)
    @ Base .\error.jl:35
  [2] add_plot_element!(lyrs::Vector{Layer}, arg::Gadfly.Guide.Title)
    @ Gadfly C:\Users\rdboylan\.julia\packages\Gadfly\OQ068\src\Gadfly.jl:191
  [3] layer(::Nothing, ::typeof(Gadfly.Geom.contour), ::Vararg{…}; mapping::@Kwargs{…})
    @ Gadfly C:\Users\rdboylan\.julia\packages\Gadfly\OQ068\src\Gadfly.jl:179
  [4] layer
    @ Gadfly C:\Users\rdboylan\.julia\packages\Gadfly\OQ068\src\Gadfly.jl:169 [inlined]
  [5] #layer#85
    @ Gadfly C:\Users\rdboylan\.julia\packages\Gadfly\OQ068\src\Gadfly.jl:188 [inlined]
  [6] layer(f::Function, xmin::Float64, xmax::Int64, ymin::Int64, ymax::Int64, elements::Gadfly.Guide.Title; mapping::@Kwargs{})
    @ Gadfly C:\Users\rdboylan\.julia\packages\Gadfly\OQ068\src\poetry.jl:122
  [7] layer
    @ Gadfly C:\Users\rdboylan\.julia\packages\Gadfly\OQ068\src\poetry.jl:107 [inlined]
  [8] plot(f::Function, xmin::Float64, xmax::Int64, ymin::Int64, ymax::Int64, elements::Gadfly.Guide.Title; mapping::@Kwargs{})
    @ Gadfly C:\Users\rdboylan\.julia\packages\Gadfly\OQ068\src\poetry.jl:75
  [9] plot(f::Function, xmin::Float64, xmax::Int64, ymin::Int64, ymax::Int64, elements::Gadfly.Guide.Title)
    @ Gadfly C:\Users\rdboylan\.julia\packages\Gadfly\OQ068\src\poetry.jl:56
 [10] top-level scope
    @ c:\Users\rdboylan\Documents\BP\linear\predictor.jl:60
Some type information was truncated. Use `show(err)` to see complete types.

Expected Behavior

My expectation was that I would get the plot with the requested title.

Speculation

Since there's only one plot, it's a little surprising to get a message of layers; I presume the plot machinery for this case is generating them or it behind the scenes.

Perhaps the somewhat unusual arguments, including the absence of a dataset, have something to do with the problem.

Context

Gadfly 1.4.0 on julia 1.10.0-beta2, running under VSCode 1.84.0.

[RossBoylan]

This, on the other hand, works:

plot(z=(x, y)->x+y/2.0, xmin=[0.1], xmax=[5], ymin=[-1], ymax=[3], Geom.contour, Guide.Title("My Title"))