Writing simple weighted digraphs

I’m using the LightGraphs package and I’m trying to write a simple weighted digraph to a file:

julia> g
{32768, 467633} directed simple Int64 graph with Float64 weights
julia> savegraph("testwt.lg",g)
1
julia> gl=loadgraph("testwt.lg")
ERROR: ArgumentError: invalid base 10 digit 'g' in "graph"
Stack trace
Stacktrace:
 [1] tryparse_internal(::Type{Int64}, ::SubString{String}, ::Int64, ::Int64, ::Int64, ::Bool) at ./parse.jl:132
 [2] #parse#347(::Nothing, ::typeof(parse), ::Type{Int64}, ::SubString{String}) at ./parse.jl:238
 [3] parse at ./parse.jl:238 [inlined]
 [4] _parse_header(::SubString{String}) at /Users/eaubanel/.julia/packages/LightGraphs/UPjU9/src/persistence/lg.jl:65
 [5] loadlg(::IOStream, ::String) at /Users/eaubanel/.julia/packages/LightGraphs/UPjU9/src/persistence/lg.jl:104
 [6] loadgraph at /Users/eaubanel/.julia/packages/LightGraphs/UPjU9/src/persistence/lg.jl:147 [inlined]
 [7] #117 at /Users/eaubanel/.julia/packages/LightGraphs/UPjU9/src/persistence/common.jl:15 [inlined]
 [8] #open#271(::Base.Iterators.Pairs{Union{},Union{},Tuple{},NamedTuple{(),Tuple{}}}, ::typeof(open), ::LightGraphs.var"#117#118"{String,LGFormat}, ::String, ::Vararg{String,N} where N) at ./io.jl:298
 [9] open at ./io.jl:296 [inlined]
 [10] loadgraph at /Users/eaubanel/.julia/packages/LightGraphs/UPjU9/src/persistence/common.jl:14 [inlined]
 [11] loadgraph(::String) at /Users/eaubanel/.julia/packages/LightGraphs/UPjU9/src/persistence/common.jl:18
 [12] top-level scope at none:0

What am I doing wrong? Reading and writing this way works fine for unweighted digraphs.