diff --git a/src/NzbDrone.Core/Indexers/Newznab/NewznabSettings.cs b/src/NzbDrone.Core/Indexers/Newznab/NewznabSettings.cs
index f45baeb01..534ed366f 100644
--- a/src/NzbDrone.Core/Indexers/Newznab/NewznabSettings.cs
+++ b/src/NzbDrone.Core/Indexers/Newznab/NewznabSettings.cs
@@ -3,6 +3,7 @@
 using System.Linq;
 using System.Text.RegularExpressions;
 using FluentValidation;
+using FluentValidation.Results;
 using NzbDrone.Common.Extensions;
 using NzbDrone.Core.Annotations;
 using NzbDrone.Core.ThingiProvider;
@@ -37,13 +38,20 @@ private static bool ShouldHaveApiKey(NewznabSettings settings)
 
         public NewznabSettingsValidator()
         {
+            Custom(newznab =>
+            {
+                if (newznab.Categories.Empty() && newznab.AnimeCategories.Empty())
+                {
+                    return new ValidationFailure("", "Either 'Categories' or 'Anime Categories' must be provided");
+                }
+
+                return null;
+            });
+
             RuleFor(c => c.Url).ValidRootUrl();
             RuleFor(c => c.ApiKey).NotEmpty().When(ShouldHaveApiKey);
-            RuleFor(c => c.Categories).NotEmpty().When(c => !c.AnimeCategories.Any());
-            RuleFor(c => c.AnimeCategories).NotEmpty().When(c => !c.Categories.Any());
-            RuleFor(c => c.AdditionalParameters)
-                .Matches(AdditionalParametersRegex)
-                .When(c => !c.AdditionalParameters.IsNullOrWhiteSpace());
+            RuleFor(c => c.AdditionalParameters).Matches(AdditionalParametersRegex)
+                                                .When(c => !c.AdditionalParameters.IsNullOrWhiteSpace());
         }
     }
 
@@ -63,16 +71,13 @@ public NewznabSettings()
         [FieldDefinition(1, Label = "API Key")]
         public String ApiKey { get; set; }
 
-        [FieldDefinition(2, Label = "Categories",
-            HelpText = "Comma Separated list, leave blank to disable standard/daily shows", Advanced = true)]
+        [FieldDefinition(2, Label = "Categories", HelpText = "Comma Separated list, leave blank to disable standard/daily shows", Advanced = true)]
         public IEnumerable<Int32> Categories { get; set; }
 
-        [FieldDefinition(3, Label = "Anime Categories", HelpText = "Comma Separated list, leave blank to disable anime",
-            Advanced = true)]
+        [FieldDefinition(3, Label = "Anime Categories", HelpText = "Comma Separated list, leave blank to disable anime", Advanced = true)]
         public IEnumerable<Int32> AnimeCategories { get; set; }
 
-        [FieldDefinition(4, Label = "Additional Parameters", HelpText = "Additional newznab parameters", Advanced = true
-            )]
+        [FieldDefinition(4, Label = "Additional Parameters", HelpText = "Additional newznab parameters", Advanced = true)]
         public String AdditionalParameters { get; set; }
 
         public NzbDroneValidationResult Validate()