Error arises when saving and loading `Accumulator`

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Julia version is 0.6 in macOS 10.12.4, the error appears like following but not sure whether it comes from JLD or DataStructures

julia> using DataStructures, JLD

julia> a = counter([2, 3, 2, 1])
DataStructures.Accumulator{Int64,Int64} with 3 entries:
  2 => 2
  3 => 1
  1 => 1

julia> save("/tmp/test.jld", "a", a)

julia> load("/tmp/test.jld", "a")
ERROR: MethodError: no method matching DataStructures.Accumulator{Int64,Int64}()
Stacktrace:
 [1] convert(::Type{DataStructures.Accumulator{Int64,Int64}}, ::JLD.AssociativeWrapper{Int64,Int64,DataStructures.Accumulator{Int64,Int64}}) at /Users/fineday/.julia/v0.6/JLD/src/JLD.jl:804
 [2] readas(::JLD.AssociativeWrapper{Int64,Int64,DataStructures.Accumulator{Int64,Int64}}) at /Users/fineday/.julia/v0.6/JLD/src/JLD.jl:795
 [3] read_scalar(::JLD.JldDataset, ::HDF5.HDF5Datatype, ::Type{T} where T) at /Users/fineday/.julia/v0.6/JLD/src/JLD.jl:409
 [4] read(::JLD.JldDataset) at /Users/fineday/.julia/v0.6/JLD/src/JLD.jl:381
 [5] read(::JLD.JldFile, ::String) at /Users/fineday/.julia/v0.6/JLD/src/JLD.jl:357
 [6] #jldopen#11(::Array{Any,1}, ::Function, ::JLD.##41#42{String}, ::String, ::Vararg{String,N} where N) at /Users/fineday/.julia/v0.6/JLD/src/JLD.jl:256
 [7] load(::FileIO.File{FileIO.DataFormat{:JLD}}, ::String) at /Users/fineday/.julia/v0.6/JLD/src/JLD.jl:1276
 [8] #load#13(::Array{Any,1}, ::Function, ::String, ::String, ::Vararg{String,N} where N) at /Users/fineday/.julia/v0.6/FileIO/src/loadsave.jl:47
 [9] load(::String, ::String) at /Users/fineday/.julia/v0.6/FileIO/src/loadsave.jl:47