ArgumentError: invalid open mode: w9

[itan1]

When using niwrite() to write a .nii.gz file I get the error:

ERROR: ArgumentError: invalid open mode: w9
Stacktrace:
 [1] open(::String, ::String; lock::Bool) at ./iostream.jl:346
 [2] open at ./iostream.jl:346 [inlined]
 [3] niwrite(::String, ::NIVolume{Float32,3,Array{UInt8,3}}) at /home/itan/projects/unet-testing/dev/NIfTI/src/NIfTI.jl:420
 [4] top-level scope at REPL[6]:1

Probably because the open mode is still "w9" from before, when gzopen() was used instead of open().