Search Version : alpha.5 (and probably alpha.6)
CMS Version : 17.1.0

When I add AddBackOfficeSearch to my startup I will get the following error during startup which prevents my website from starting up

Unhandled exception. System.MissingMethodException: Method not found: 'Void Umbraco.Extensions.ServiceCollectionExtensions.AddUnique(Microsoft.Extensions.DependencyInjection.IServiceCollection)'.
at Umbraco.Cms.Search.BackOffice.DependencyInjection.UmbracoBuilderExtensions.AddBackOfficeSearch(IUmbracoBuilder builder)
at Umbraco.Cms.Search.BackOffice.DependencyInjection.UmbracoBuilderExtensions.AddBackOfficeSearch(IUmbracoBuilder builder)
at ZGT.Infrastructure.Extensions.UmbracoBuilderExtensions.SetupSearch(IUmbracoBuilder builder) in C:\projects\ZGT\backend\code\ZGT.Infrastructure\Extensions\UmbracoBuilderExtensions.cs:line 187
at ZGT.Infrastructure.Extensions.UmbracoBuilderExtensions.AddInfrastructure(IUmbracoBuilder builder) in C:\projects\ZGT\backend\code\ZGT.Infrastructure\Extensions\UmbracoBuilderExtensions.cs:line 45
at ZGT.Infrastructure.InfrastructureComposer.Compose(IUmbracoBuilder builder) in C:\projects\ZGT\backend\code\ZGT.Infrastructure\InfrastructureComposer.cs:line 11
at Umbraco.Cms.Core.Composing.ComposerGraph.Compose()
at Umbraco.Cms.Core.DependencyInjection.UmbracoBuilderExtensions.AddComposers(IUmbracoBuilder builder)
at Program.

$(String[] args) in C:\projects\ZGT\backend\code\ZGT.Website\Program.cs:line 12
at Program.(String[] args)