# Error when using strawberry fields gaussian backend (ContextualVersionConflict)

**URL:** <https://discuss.pennylane.ai/t/error-when-using-strawberry-fields-gaussian-backend-contextualversionconflict/822>\
**Category:** PennyLane Help\
**Created:** [February 5, 2021, 4:27pm UTC](https://discuss.pennylane.ai/t/error-when-using-strawberry-fields-gaussian-backend-contextualversionconflict/822 "2021-02-05T16:27:02Z")\
**Posts on this page:** 4\
**Page:** 1

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**Author:** ![kannan\_v](https://yyz2.discourse-cdn.com/flex012/user_avatar/discuss.pennylane.ai/kannan_v/32/428_2.png) [@kannan\_v](https://discuss.pennylane.ai/u/kannan_v)\
**Post date:** [February 5, 2021, 4:27pm UTC](https://discuss.pennylane.ai/t/error-when-using-strawberry-fields-gaussian-backend-contextualversionconflict/822/1 "2021-02-05T16:27:02Z")

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Hello,

I was trying to use the gaussian backend as in the GBS tutorial ([https://pennylane.ai/qml/demos/tutorial\_gbs.html](https://pennylane.ai/qml/demos/tutorial_gbs.html)) but I’m getting the following error:

**ContextualVersionConflict: (numba 0.45.1 (c:\users\kannan\anaconda3\lib\site-packages), Requirement.parse(‘numba\>=0.49.1’), {‘thewalrus’})**

How can I fix this? Both Pennylane and StrawberryFields have been updated to the latest version.

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**Author:** ![antalszava](https://yyz2.discourse-cdn.com/flex012/user_avatar/discuss.pennylane.ai/antalszava/32/171_2.png) [@antalszava](https://discuss.pennylane.ai/u/antalszava)\
**Post date:** [February 5, 2021, 7:26pm UTC](https://discuss.pennylane.ai/t/error-when-using-strawberry-fields-gaussian-backend-contextualversionconflict/822/2 "2021-02-05T19:26:15Z")

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Hi @kannan_v,

That is odd! 🤔 Did you install PennyLane and Strawberry Fields via `pip install pennylane strawberryfields`? Fresh installs would generally have to pull a greater version of `numba` than that, so wondering what it could come down to. 🤔

You could run `pip install numba --upgrade` as a fix to update the numba version that you have.

Let us know how this works out! 🙂

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**Author:** ![kannan\_v](https://yyz2.discourse-cdn.com/flex012/user_avatar/discuss.pennylane.ai/kannan_v/32/428_2.png) [@kannan\_v](https://discuss.pennylane.ai/u/kannan_v)\
**Post date:** [February 8, 2021, 2:20pm UTC](https://discuss.pennylane.ai/t/error-when-using-strawberry-fields-gaussian-backend-contextualversionconflict/822/3 "2021-02-08T14:20:38Z")

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Hello @antalszava,

Thank very you for the suggestion.  
When I do tried to update numba, I was faced with this error:

_ERROR: Cannot uninstall ‘llvmlite’. It is a distutils installed project and thus we cannot accurately determine which files belong to it which would lead to only a partial uninstall._

This was then solved by giving the `--user` tag to the command as:  
`pip install numba --upgrade --user` and that solved the issue!

Now I’m able to use the Strawberry Fields gaussian backend 🙂

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<div class="post-metadata">

**Author:** ![antalszava](https://yyz2.discourse-cdn.com/flex012/user_avatar/discuss.pennylane.ai/antalszava/32/171_2.png) [@antalszava](https://discuss.pennylane.ai/u/antalszava)\
**Post date:** [February 8, 2021, 2:29pm UTC](https://discuss.pennylane.ai/t/error-when-using-strawberry-fields-gaussian-backend-contextualversionconflict/822/4 "2021-02-08T14:29:59Z")

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Hi @kannan_v,

Great to hear! Thanks for the clarification, it’ll be helpful for other people too.