# ERROR: UndefVarError: AbstractEnsembleSolution not defined

**URL:** <https://discourse.julialang.org/t/error-undefvarerror-abstractensemblesolution-not-defined/29283>\
**Category:** General Usage\
**Tags:** question\
**Created:** [September 29, 2019, 3:18am UTC](https://discourse.julialang.org/t/error-undefvarerror-abstractensemblesolution-not-defined/29283 "2019-09-29T03:18:54Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![Matthew\_Overlin](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/matthew_overlin/32/10533_2.png) [@Matthew\_Overlin](https://discourse.julialang.org/u/Matthew_Overlin)\
**Post date:** [September 29, 2019, 3:18am UTC](https://discourse.julialang.org/t/error-undefvarerror-abstractensemblesolution-not-defined/29283/1 "2019-09-29T03:18:54Z")

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Hello. I get this error when I run this line: result = Optim.optimize(obj, [1.0,0.5], Optim.BFGS()). I am following an example at this web page: [https://docs.juliadiffeq.org/latest/analysis/parameter\_estimation.html](https://docs.juliadiffeq.org/latest/analysis/parameter_estimation.html)

I believe I have all of the correct packages installed, of my installed packages below:  
DiffEqBase v5.6.4  
DiffEqParamEstim v1.7.1  
DifferentialEquations v6.3.0  
GR v0.39.1  
Gadfly v1.0.1  
IJulia v1.18.1  
Interact v0.10.2  
LaTeXStrings v1.0.3  
Optim v0.19.3  
Plots v0.24.0  
PyPlot v2.8.1  
RecursiveArrayTools v0.20.0  
StochasticDiffEq v6.7.0  
Sundials v3.3.0

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<div class="post-metadata">

**Author:** ![ChrisRackauckas](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/chrisrackauckas/32/77_2.png) [@ChrisRackauckas](https://discourse.julialang.org/u/ChrisRackauckas)\
**Post date:** [September 29, 2019, 4:48am UTC](https://discourse.julialang.org/t/error-undefvarerror-abstractensemblesolution-not-defined/29283/2 "2019-09-29T04:48:27Z")

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Your issue is that you are on a very old version of DiffEqBase.jl. Could you try `]up` to update your packages?

Note: this is probably the reason for [Unable to precompile ParameterizedFunctions](https://discourse.julialang.org/t/unable-to-precompile-parameterizedfunctions/29284) as well.