Using ArbFloat fails at subtraction / addition of Dual and ArbFloat

Hello, I cannot use jacobian with ArbFloat type. The following code runs when T = Float64

using ArbFloats
using ForwardDiff

T = Float64 # ArbFloat
M = 3

F = [T(0.0) for i in 1:M]
x0 = [T(-1.0) for i in 1:M]

function f!(F,x)
  for i in eachindex(F)
    F[i] = x[i] - T(1.0)
  end
end

ForwardDiff.jacobian(f!,F,x0)

but fails when I set T = ArbFloat with the following error:

ERROR: LoadError: MethodError: +(::ForwardDiff.Dual{ForwardDiff.Tag{#f!,ArbFloats.ArbFloat{116}},ArbFloats.ArbFloat{116},3}, ::ArbFloats.ArbFloat{116}) is ambiguous. Candidates:
  +(x::ForwardDiff.Dual{Tx,V,N} where N where V<:Real, y::AbstractFloat) where Tx in ForwardDiff at /home/gluon/.julia/v0.6/ForwardDiff/src/dual.jl:103
  +(x::ForwardDiff.Dual{Tx,V,N} where N where V<:Real, y::Real) where Tx in ForwardDiff at /home/gluon/.julia/v0.6/ForwardDiff/src/dual.jl:103
  +(x::R, y::T) where {T<:ArbFloats.ArbFloat, R<:Real} in ArbFloats at /home/gluon/.julia/v0.6/ArbFloats/src/math/arith.jl:60
Possible fix, define
  +(::ForwardDiff.Dual{Tx,V,N} where N where V<:Real, ::T<:ArbFloats.ArbFloat)
Stacktrace:
 [1] (::Atom.##110#114{String,String})() at /home/gluon/.julia/v0.6/Atom/src/eval.jl:104
 [2] withpath(::Atom.##110#114{String,String}, ::String) at /home/gluon/.julia/v0.6/CodeTools/src/utils.jl:30
 [3] withpath(::Function, ::String) at /home/gluon/.julia/v0.6/Atom/src/eval.jl:38
 [4] didWriteToREPL(::Atom.##109#113{String,String}) at /home/gluon/.julia/v0.6/Atom/src/repl.jl:129
 [5] hideprompt(::Atom.##109#113{String,String}) at /home/gluon/.julia/v0.6/Atom/src/repl.jl:65
 [6] macro expansion at /home/gluon/.julia/v0.6/Atom/src/eval.jl:99 [inlined]
 [7] (::Atom.##108#112{Dict{String,Any}})() at ./task.jl:80
while loading /media/DATA/PhD/code/sandbox/sandbox.jl, in expression starting on line 57

This is just a test code which I produced to show the error, the actual code is different but leads to same kind of errors. Can someone say me what is going on here and how to fix this? Thanks.

Start by running the reproducer with T = ArbFloat and inspect the conflicting methods in ForwardDiff/src/dual.jl and ArbFloats/src/math/arith.jl. Trace the subtraction or addition dispatch involved in ForwardDiff.jacobian, then verify that the example completes without an ambiguous-method error.