# Error in example: Parameter Estimation on Highly Stiff Systems

**URL:** <https://discourse.julialang.org/t/error-in-example-parameter-estimation-on-highly-stiff-systems/93229>\
**Category:** Optimization (Mathematical)\
**Tags:** diffeq, optimization\
**Created:** [January 19, 2023, 7:48pm UTC](https://discourse.julialang.org/t/error-in-example-parameter-estimation-on-highly-stiff-systems/93229 "2023-01-19T19:48:41Z")\
**Posts on this page:** 1\
**Page:** 1

<div class="post-metadata">

**Author:** ![kaido975](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/kaido975/32/36862_2.png) [@kaido975](https://discourse.julialang.org/u/kaido975)\
**Post date:** [January 19, 2023, 7:48pm UTC](https://discourse.julialang.org/t/error-in-example-parameter-estimation-on-highly-stiff-systems/93229/1 "2023-01-19T19:48:41Z")

</div>

The example provided at [Parameter Estimation on Highly Stiff Systems · SciMLSensitivity.jl](https://docs.sciml.ai/SciMLSensitivity/stable/ode_fitting/stiff_ode_fit/), does not seem to be working with Optimization.jl but works fine with DiffEqFlux.sciml\_train. I am getting the following error with Optimization.jl.

```julia
ERROR: MethodError: no method matching +(::Base.RefValue{Any}, ::NamedTuple{(:contents,), Tuple{Matrix{Float64}}})

```