diff --git a/src/Microsoft.VisualStudio.ProjectSystem.Managed/ProjectSystem/LanguageServices/LanguageServiceHost.cs b/src/Microsoft.VisualStudio.ProjectSystem.Managed/ProjectSystem/LanguageServices/LanguageServiceHost.cs
index 2968f2a91af..903cba19638 100644
--- a/src/Microsoft.VisualStudio.ProjectSystem.Managed/ProjectSystem/LanguageServices/LanguageServiceHost.cs
+++ b/src/Microsoft.VisualStudio.ProjectSystem.Managed/ProjectSystem/LanguageServices/LanguageServiceHost.cs
@@ -136,6 +136,8 @@ protected override async Task InitializeCoreAsync(CancellationToken cancellation
                 linkOptions: DataflowOption.PropagateCompletion,
                 cancellationToken: cancellationToken),
 
+            ProjectDataSources.JoinUpstreamDataSources(_joinableTaskFactory, _projectFaultHandler, _activeConfiguredProjectProvider, _activeConfigurationGroupSubscriptionService),
+
             new DisposableDelegate(() =>
             {
                 // Dispose all workspaces. Note that this happens within a lock, so we will not race with project updates.