diff --git a/src/NzbDrone.Common/Extensions/StringExtensions.cs b/src/NzbDrone.Common/Extensions/StringExtensions.cs
index 1ec592515..be7441941 100644
--- a/src/NzbDrone.Common/Extensions/StringExtensions.cs
+++ b/src/NzbDrone.Common/Extensions/StringExtensions.cs
@@ -1,5 +1,6 @@
 using System;
 using System.Collections.Generic;
+using System.Diagnostics.CodeAnalysis;
 using System.Linq;
 using System.Net;
 using System.Net.Sockets;
@@ -93,15 +94,17 @@ public static string CleanSpaces(this string text)
             return CollapseSpace.Replace(text, " ").Trim();
         }
 
-        public static bool IsNullOrWhiteSpace(this string text)
+        #nullable enable
+        public static bool IsNullOrWhiteSpace([NotNullWhen(false)] this string? text)
         {
             return string.IsNullOrWhiteSpace(text);
         }
 
-        public static bool IsNotNullOrWhiteSpace(this string text)
+        public static bool IsNotNullOrWhiteSpace([NotNullWhen(true)] this string? text)
         {
             return !string.IsNullOrWhiteSpace(text);
         }
+        #nullable disable
 
         public static bool StartsWithIgnoreCase(this string text, string startsWith)
         {
diff --git a/src/Sonarr.Api.V5/Series/SeriesFolderAsRootFolderValidator.cs b/src/Sonarr.Api.V5/Series/SeriesFolderAsRootFolderValidator.cs
index 4167cf522..408fba8d9 100644
--- a/src/Sonarr.Api.V5/Series/SeriesFolderAsRootFolderValidator.cs
+++ b/src/Sonarr.Api.V5/Series/SeriesFolderAsRootFolderValidator.cs
@@ -34,7 +34,7 @@ protected override bool IsValid(PropertyValidatorContext context)
             return true;
         }
 
-        var rootFolder = new DirectoryInfo(rootFolderPath!).Name;
+        var rootFolder = new DirectoryInfo(rootFolderPath).Name;
         var series = seriesResource.ToModel();
         var seriesFolder = _fileNameBuilder.GetSeriesFolder(series);