# JLD2 Error: "type DataType has no field mutable"

**URL:** <https://discourse.julialang.org/t/jld2-error-type-datatype-has-no-field-mutable/78651>\
**Category:** New to Julia\
**Tags:** jld2\
**Created:** [March 29, 2022, 3:21am UTC](https://discourse.julialang.org/t/jld2-error-type-datatype-has-no-field-mutable/78651 "2022-03-29T03:21:06Z")\
**Posts on this page:** 5\
**Page:** 1

<div class="post-metadata">

**Author:** ![poopsilon](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/poopsilon/32/35351_2.png) [@poopsilon](https://discourse.julialang.org/u/poopsilon)\
**Post date:** [March 29, 2022, 3:21am UTC](https://discourse.julialang.org/t/jld2-error-type-datatype-has-no-field-mutable/78651/1 "2022-03-29T03:21:06Z")

</div>

I’d like to save variables for later. To do this, I installed the JLD2 package. But when I try to save, I get the following error:

> **Error Details**
>
> ```julia
> julia> using JLD2
> 
> julia> hello = "world"
> "world"
> 
> julia> foo = :bar
> :bar
> 
> julia> @save "example.jld2" hello foo
> ERROR: type DataType has no field mutable
> Stacktrace:
> [1] getproperty
> @ .\Base.jl:37 [inlined]
> [2] ismutabletype(x::DataType)
> @ JLD2 C:\Users\USER\.julia\packages\JLD2\qncOK\src\datasets.jl:538
> [3] write_dataset(f::JLD2.JLDFile{JLD2.MmapIO}, dataspace::JLD2.WriteDataspace{0, Tuple{}}, datatype::JLD2.BasicDatatype, odr::JLD2.FixedLengthString{String}, data::String, wsession::JLD2.JLDWriteSession{Dict{UInt64, JLD2.RelOffset}})
> @ JLD2 C:\Users\USER\.julia\packages\JLD2\qncOK\src\datasets.jl:428
> [4] write_dataset
> @ C:\Users\USER\.julia\packages\JLD2\qncOK\src\datasets.jl:542 [inlined]
> [5] write(g::JLD2.Group{JLD2.JLDFile{JLD2.MmapIO}}, name::String, obj::String, wsession::JLD2.JLDWriteSession{Dict{UInt64, JLD2.RelOffset}})
> @ JLD2 C:\Users\USER\.julia\packages\JLD2\qncOK\src\groups.jl:119
> [6] write(f::JLD2.JLDFile{JLD2.MmapIO}, name::String, obj::String, wsession::JLD2.JLDWriteSession{Dict{UInt64, JLD2.RelOffset}})
> @ JLD2 C:\Users\USER\.julia\packages\JLD2\qncOK\src\JLD2.jl:347
> [7] top-level scope
> @ C:\Users\USER\.julia\packages\JLD2\qncOK\src\loadsave.jl:66
> 
> ```

What’s going wrong and what can I do to fix this? Did I do something wrong? Is there a better way to save variables for later?

---

<div class="post-metadata">

**Author:** ![JonasIsensee](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/jonasisensee/32/4704_2.png) [@JonasIsensee](https://discourse.julialang.org/u/JonasIsensee)\
**Post date:** [March 29, 2022, 5:06am UTC](https://discourse.julialang.org/t/jld2-error-type-datatype-has-no-field-mutable/78651/2 "2022-03-29T05:06:59Z")

</div>

Hi,

this is an issue that was fixed quite some time ago.

Can you please try to update JLD2 to the latest version?  
What julia version are you using?

---

<div class="post-metadata">

**Author:** ![poopsilon](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/poopsilon/32/35351_2.png) [@poopsilon](https://discourse.julialang.org/u/poopsilon)\
**Post date:** [March 29, 2022, 12:24pm UTC](https://discourse.julialang.org/t/jld2-error-type-datatype-has-no-field-mutable/78651/3 "2022-03-29T12:24:17Z")

</div>

I’m running

```julia
julia> VERSION
v"1.7.2"

```

I tried `pkg> update` and `pkg> up JLD2`, but it didn’t seem to fix my issue. The JLD2 version is

```julia
JLD2 v0.4.3

```

---

<div class="post-metadata">

**Author:** ![JonasIsensee](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/jonasisensee/32/4704_2.png) [@JonasIsensee](https://discourse.julialang.org/u/JonasIsensee)\
**Post date:** [March 29, 2022, 12:28pm UTC](https://discourse.julialang.org/t/jld2-error-type-datatype-has-no-field-mutable/78651/4 "2022-03-29T12:28:13Z")

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Hi @poopsilon ,  
ok, then the JLD2 version is definitely the reason you’re seeing the error message.  
The latest release of JLD2 is `v0.4.22`.

Therefore the “real” issue is that something is holding back your versions.  
You might try to uninstall JLD2 and reinstall and check if you have “pinned” any versions explicitly.

---

<div class="post-metadata">

**Author:** ![poopsilon](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/poopsilon/32/35351_2.png) [@poopsilon](https://discourse.julialang.org/u/poopsilon)\
**Post date:** [March 29, 2022, 12:56pm UTC](https://discourse.julialang.org/t/jld2-error-type-datatype-has-no-field-mutable/78651/5 "2022-03-29T12:56:29Z")

</div>

Thanks for your help!

I uninstalled JLD2 and reinstalled `v0.4.22` from the github link in [this page](https://juliahub.com/ui/Packages/JLD2/O1EyT/0.4.22). Seems to be working now. Not sure how I got the wrong version though…