# Dash JSON3 error

**URL:** <https://discourse.julialang.org/t/dash-json3-error/74829>\
**Category:** Visualization\
**Tags:** json3, dash\
**Created:** [January 18, 2022, 8:29pm UTC](https://discourse.julialang.org/t/dash-json3-error/74829 "2022-01-18T20:29:48Z")\
**Posts on this page:** 1\
**Page:** 1

<div class="post-metadata">

**Author:** ![Iulian.Cioarca](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/iulian.cioarca/32/30166_2.png) [@Iulian.Cioarca](https://discourse.julialang.org/u/Iulian.Cioarca)\
**Post date:** [January 18, 2022, 8:29pm UTC](https://discourse.julialang.org/t/dash-json3-error/74829/1 "2022-01-18T20:29:48Z")

</div>

I recently updated to Julia 1.7.1 and along with it some packages. My previously working Dash app now crashes with the following error when I want to plot something:

```julia
┌ Error: error handling request
│ exception =
│ ArgumentError: JSON.Writer.CompositeTypeWrapper{NamedTuple{(:font, :font_family), Tuple{NamedTuple{(:size,), Tuple{Int64}}, String}}} doesn't have a defined `StructTypes.StructType`
│ Stacktrace:
│ [1] write(::StructTypes.NoStructType, buf::Vector{UInt8}, pos::Int64, len::Int64, ::JSON.Writer.CompositeTypeWrapper{NamedTuple{(:font, :font_family), Tuple{NamedTuple{(:size,), Tuple{Int64}}, String}}}; kw::Base.Pairs{Symbol, Union{}, Tuple{}, NamedTuple{(), Tuple{}}})
│ @ JSON3 C:\Users\cioarca\.julia\packages\JSON3\tqMvg\src\write.jl:91
│ [2] write(::StructTypes.NoStructType, buf::Vector{UInt8}, pos::Int64, len::Int64, ::JSON.Writer.CompositeTypeWrapper{NamedTuple{(:font, :font_family), Tuple{NamedTuple{(:size,), Tuple{Int64}}, String}}})
│ @ JSON3 C:\Users\cioarca\.julia\packages\JSON3\tqMvg\src\write.jl:91
│ [3] write(::StructTypes.DictType, buf::Vector{UInt8}, pos::Int64, len::Int64, x::Dict{Any, Any}; kw::Base.Pairs{Symbol, Union{}, Tuple{}, NamedTuple{(), Tuple{}}})
│ @ JSON3 C:\Users\cioarca\.julia\packages\JSON3\tqMvg\src\write.jl:155
│ [4] write(::StructTypes.DictType, buf::Vector{UInt8}, pos::Int64, len::Int64, x::Dict{Any, Any})
│ @ JSON3 C:\Users\cioarca\.julia\packages\JSON3\tqMvg\src\write.jl:146
│ [5] write(::StructTypes.DictType, buf::Vector{UInt8}, pos::Int64, len::Int64, x::Dict{Symbol, Any}; kw::Base.Pairs{Symbol, Union{}, Tuple{}, NamedTuple{(), Tuple{}}})
│ @ JSON3 C:\Users\cioarca\.julia\packages\JSON3\tqMvg\src\write.jl:155
│ [6] write(::StructTypes.DictType, buf::Vector{UInt8}, pos::Int64, len::Int64, x::Dict{Symbol, Any})
│ @ JSON3 C:\Users\cioarca\.julia\packages\JSON3\tqMvg\src\write.jl:146
│ [7] write(::StructTypes.DictType, buf::Vector{UInt8}, pos::Int64, len::Int64, x::Dict{Symbol, Any}; kw::Base.Pairs{Symbol, Union{}, Tuple{}, NamedTuple{(), Tuple{}}})
│ @ JSON3 C:\Users\cioarca\.julia\packages\JSON3\tqMvg\src\write.jl:155

```

Dash version is 1.1.1. I’m also using JSON package (I suspect JSON3 is used by Dash as dependency).  
Any hints for solving this?