diff --git a/ErsatzTV.Tests/Controllers/RerunCollectionControllerTests.cs b/ErsatzTV.Tests/Controllers/RerunCollectionControllerTests.cs
index 3da210db6..9a6430775 100644
--- a/ErsatzTV.Tests/Controllers/RerunCollectionControllerTests.cs
+++ b/ErsatzTV.Tests/Controllers/RerunCollectionControllerTests.cs
@@ -155,6 +155,22 @@ public class RerunCollectionControllerTests
         result.ShouldBeOfType<UnprocessableEntityObjectResult>();
     }
 
+    [Test]
+    public async Task Create_Should_Return_422_For_Unsupported_Collection_Type()
+    {
+        IActionResult result = await _controller.Create(
+            new CreateRerunCollectionRequest(
+                "Nightly",
+                CollectionType.Playlist,
+                1,
+                PlaybackOrder.Chronological,
+                PlaybackOrder.Chronological),
+            CancellationToken.None);
+
+        result.ShouldBeOfType<UnprocessableEntityObjectResult>();
+        await _mediator.DidNotReceive().Send(Arg.Any<CreateRerunCollection>(), Arg.Any<CancellationToken>());
+    }
+
     [Test]
     public async Task Update_Should_Return_200_With_Refreshed_Body_And_Resolve_Selection()
     {
@@ -206,6 +222,23 @@ public class RerunCollectionControllerTests
         await _mediator.DidNotReceive().Send(Arg.Any<GetRerunCollectionById>(), Arg.Any<CancellationToken>());
     }
 
+    [Test]
+    public async Task Update_Should_Return_422_For_Unsupported_Collection_Type()
+    {
+        IActionResult result = await _controller.Update(
+            4,
+            new UpdateRerunCollectionRequest(
+                "Nightly",
+                CollectionType.RerunFirstRun,
+                1,
+                PlaybackOrder.Chronological,
+                PlaybackOrder.Chronological),
+            CancellationToken.None);
+
+        result.ShouldBeOfType<UnprocessableEntityObjectResult>();
+        await _mediator.DidNotReceive().Send(Arg.Any<UpdateRerunCollection>(), Arg.Any<CancellationToken>());
+    }
+
     [Test]
     public async Task Delete_Should_Return_204_On_Success()
     {
diff --git a/ErsatzTV/Controllers/Api/Requests/RerunCollectionRequestMapping.cs b/ErsatzTV/Controllers/Api/Requests/RerunCollectionRequestMapping.cs
index c5b215aae..61899bca8 100644
--- a/ErsatzTV/Controllers/Api/Requests/RerunCollectionRequestMapping.cs
+++ b/ErsatzTV/Controllers/Api/Requests/RerunCollectionRequestMapping.cs
@@ -14,6 +14,27 @@ namespace ErsatzTV.Controllers.Api.Requests;
 // doing extra lookup queries. The remaining VMs are left null (the handler expects that).
 internal static class RerunCollectionRequestMapping
 {
+    /// <summary>
+    ///     The only <see cref="CollectionType" /> values valid as a rerun collection's selected
+    ///     source. Excludes Playlist / RerunFirstRun / RerunRerun / SearchQuery / Fake* — those
+    ///     are not media-item-backed collection types and must not be resolved via
+    ///     <see cref="ResolveSelection" />. Callers (the controller) must check this first.
+    /// </summary>
+    public static bool IsSupportedSelectionType(CollectionType collectionType) =>
+        collectionType is CollectionType.Collection
+            or CollectionType.MultiCollection
+            or CollectionType.SmartCollection
+            or CollectionType.TelevisionShow
+            or CollectionType.TelevisionSeason
+            or CollectionType.Artist
+            or CollectionType.Movie
+            or CollectionType.Episode
+            or CollectionType.MusicVideo
+            or CollectionType.OtherVideo
+            or CollectionType.Song
+            or CollectionType.Image
+            or CollectionType.RemoteStream;
+
     public static (MediaCollectionViewModel Collection,
         MultiCollectionViewModel MultiCollection,
         SmartCollectionViewModel SmartCollection,
@@ -43,7 +64,9 @@ internal static class RerunCollectionRequestMapping
 
             // Any media-item-backed collection type (TelevisionShow, TelevisionSeason,
             // Artist, Movie, Episode, MusicVideo, OtherVideo, Song, Image, ...) resolves to
-            // the MediaItem VM keyed by media item id.
+            // the MediaItem VM keyed by media item id. The caller (RerunCollectionController)
+            // has already validated CollectionType via IsSupportedSelectionType, so this
+            // catch-all only ever receives a real media-item type.
             _ => (
                 null,
                 null,
diff --git a/ErsatzTV/Controllers/Api/RerunCollectionController.cs b/ErsatzTV/Controllers/Api/RerunCollectionController.cs
index ffb542d82..6faa54031 100644
--- a/ErsatzTV/Controllers/Api/RerunCollectionController.cs
+++ b/ErsatzTV/Controllers/Api/RerunCollectionController.cs
@@ -62,6 +62,13 @@ public class RerunCollectionController(IMediator mediator) : ControllerBase
         [Required] [FromBody] CreateRerunCollectionRequest request,
         CancellationToken cancellationToken)
     {
+        if (!RerunCollectionRequestMapping.IsSupportedSelectionType(request.CollectionType))
+        {
+            return BaseError.New(
+                $"Unsupported collection type '{request.CollectionType}' for a rerun collection")
+                .ToErrorResult();
+        }
+
         Either<BaseError, RerunCollectionViewModel> result =
             await mediator.Send(request.ToCommand(), cancellationToken);
         return result.ToCreatedResult(
@@ -81,6 +88,13 @@ public class RerunCollectionController(IMediator mediator) : ControllerBase
         [Required] [FromBody] UpdateRerunCollectionRequest request,
         CancellationToken cancellationToken)
     {
+        if (!RerunCollectionRequestMapping.IsSupportedSelectionType(request.CollectionType))
+        {
+            return BaseError.New(
+                $"Unsupported collection type '{request.CollectionType}' for a rerun collection")
+                .ToErrorResult();
+        }
+
         Either<BaseError, Unit> result = await mediator.Send(request.ToCommand(id), cancellationToken);
         return await result.Match(
             Left: error => Task.FromResult(error.ToErrorResult()),