diff --git a/src/ProjectTemplates/Microsoft.Extensions.AI.Templates/templates/AIChatWeb-CSharp/AIChatWeb-CSharp.Web/Components/Pages/Chat/Chat.razor b/src/ProjectTemplates/Microsoft.Extensions.AI.Templates/templates/AIChatWeb-CSharp/AIChatWeb-CSharp.Web/Components/Pages/Chat/Chat.razor
index 6fc5881c18f..717badc342e 100644
--- a/src/ProjectTemplates/Microsoft.Extensions.AI.Templates/templates/AIChatWeb-CSharp/AIChatWeb-CSharp.Web/Components/Pages/Chat/Chat.razor
+++ b/src/ProjectTemplates/Microsoft.Extensions.AI.Templates/templates/AIChatWeb-CSharp/AIChatWeb-CSharp.Web/Components/Pages/Chat/Chat.razor
@@ -121,7 +121,7 @@
     [Description("Searches for information using a phrase or keyword. Relies on documents already being loaded.")]
     private async Task<IEnumerable<string>> SearchAsync(
         [Description("The phrase to search for.")] string searchPhrase,
-        [Description("If possible, specify the filename to search that file only. If not provided or empty, the search includes all files.")] string? filenameFilter = null)
+        [Description("If possible, specify the filename to search that file only. If not provided or empty, the search includes all files.")] string filenameFilter = "")
     {
         await InvokeAsync(StateHasChanged);
         var results = await Search.SearchAsync(searchPhrase, filenameFilter, maxResults: 5);