no method matching + error

[tk3369]

Reading larger file via iteration over CSV.File yields error:

julia> makecsv(filename, n) = open(filename, "w") do io
           println(io,"a")
           foreach(x->println(io,x), 1:n)
       end;

julia> readcsv(filename) = let f = CSV.File(filename)
           total = 0
           for (i,row) in enumerate(f)
               total += row.a
           end
           return total
       end;

julia> makecsv("tom.csv", 1000); readcsv("tom.csv")
500500

julia> makecsv("tom.csv", 100000); readcsv("tom.csv")
ERROR: MethodError: no method matching +(::Tuple{Int64,Int64,Int64,NTuple{4,CSV.Column{Int64,Int64}}}, ::Int64)
Closest candidates are:
  +(::Any, ::Any, ::Any, ::Any...) at operators.jl:529
  +(::Complex{Bool}, ::Real) at complex.jl:297
  +(::Missing, ::Number) at missing.jl:115
  ...
Stacktrace:
 [1] iterate(::Base.Iterators.Enumerate{CSV.File}, ::Tuple{Int64,Tuple{Int64,Int64,Int64,NTuple{4,CSV.Column{Int64,Int64}}}}) at /Users/tomkwong/.julia/packages/CSV/skXyc/src/iteration.jl:48
 [2] readcsv(::String) at ./REPL[18]:4
 [3] top-level scope at REPL[22]:1

My versions:

CSV v0.5.18

julia> versioninfo()
Julia Version 1.3.0
Commit 46ce4d7933 (2019-11-26 06:09 UTC)
Platform Info:
  OS: macOS (x86_64-apple-darwin19.0.0)
  CPU: Intel(R) Core(TM) i5-4258U CPU @ 2.40GHz
  WORD_SIZE: 64
  LIBM: libopenlibm
  LLVM: libLLVM-6.0.1 (ORCJIT, haswell)
Environment:
  JULIA_NUM_THREADS = 4

[tk3369]

Strangely enough. I cannot replicate anymore.... Leaving issue open just in case that there's additional insight about what might have happened.