I noticed this in recent troubleshooting of an internal issue on our build boxes (we don't use the hosted agents) Seems that this default value https://github.com/pester/AzureDevOpsExtension/blob/a44ff1dc8cf8a4c669516039cf8f39b3dff9dfcd/Extension/PesterTask/PesterV9/Pester.ps1#L43 will then have an impact on potentially importing pester at this point https://github.com/pester/AzureDevOpsExtension/blob/a44ff1dc8cf8a4c669516039cf8f39b3dff9dfcd/Extension/PesterTask/PesterV9/Pester.ps1#L61 I propose to fix this with some additional defensive coding just to be sure that Pester v5 will never accidentally import