twinx() and fgcolor issue

I'm having an error when using pyplot backend, and twinx().
If I modify the backgroud color and try to use twinx() to have 2 y axes, I get the following error:
ERROR: UndefVarError: fgcolor not defined.
I'm using Arch linux and I installed Julia from the AUR package julia-bin.

Below is a minimum example to reproduce the error:
```julia
using Plots
using LaTeXStrings
pyplot()

plot_font = "CMU Typewriter Text"

default(fontfamily=plot_font,
linewidth=2, framestyle=:box,
label=nothing, grid=true, minorgrid=true,
minorgridls=:dot, gridls=:dash,
gridlw=1, minorgridlw=0.75,
background_color=RGB(7/255,54/255,66/255),
# fgcolor=RGB(255/255,255/255,255/255),
right_margin=15Plots.mm,
bottom_margin=5Plots.mm
)

a = 1:10
b = rand(10)
plot(a,b, label = L"randData", ylabel = "Rand data",color = :red, legend = :topleft)
p = twinx()
plot!(p,a,log.(a), label = L"log(x)", legend = :topright, ylabel = "The right Y label",
xlabel = "numbers")
#savefig("test")
gui()```