diff --git a/src/Umbraco.Core/Services/ContentTypeEditing/ContentTypeEditingServiceBase.cs b/src/Umbraco.Core/Services/ContentTypeEditing/ContentTypeEditingServiceBase.cs
index 00708fb439..b1847c80da 100644
--- a/src/Umbraco.Core/Services/ContentTypeEditing/ContentTypeEditingServiceBase.cs
+++ b/src/Umbraco.Core/Services/ContentTypeEditing/ContentTypeEditingServiceBase.cs
@@ -1,4 +1,4 @@
-using Umbraco.Cms.Core.Models;
+using Umbraco.Cms.Core.Models;
 using Umbraco.Cms.Core.Models.ContentTypeEditing;
 using Umbraco.Cms.Core.Services.OperationStatus;
 using Umbraco.Cms.Core.Strings;
@@ -407,7 +407,7 @@ internal abstract class ContentTypeEditingServiceBase<TContentType, TContentType
     }
 
     // This this method gets aliases across documents, members, and media, so it covers it all
-    private bool ContentTypeAliasIsInUse(string alias) => _contentTypeService.GetAllContentTypeAliases().Contains(alias);
+    private bool ContentTypeAliasIsInUse(string alias) => _contentTypeService.GetAllContentTypeAliases().InvariantContains(alias);
 
     private bool ContentTypeAliasCanBeUsedFor(string alias, Guid key)
     {
diff --git a/tests/Umbraco.Tests.Integration/Umbraco.Core/Services/ContentTypeEditingServiceTests.Create.cs b/tests/Umbraco.Tests.Integration/Umbraco.Core/Services/ContentTypeEditingServiceTests.Create.cs
index 814d1b5be7..a987e9a4f7 100644
--- a/tests/Umbraco.Tests.Integration/Umbraco.Core/Services/ContentTypeEditingServiceTests.Create.cs
+++ b/tests/Umbraco.Tests.Integration/Umbraco.Core/Services/ContentTypeEditingServiceTests.Create.cs
@@ -861,14 +861,15 @@ internal sealed partial class ContentTypeEditingServiceTests
         Assert.AreEqual(ContentTypeOperationStatus.InvalidAlias, result.Status);
     }
 
-    [Test]
-    public async Task Cannot_Use_Existing_Alias()
+    [TestCase("test")] // Matches alias case sensitively.
+    [TestCase("Test")] // Matches alias case insensitively.
+    public async Task Cannot_Use_Existing_Alias(string newAlias)
     {
         var createModel = ContentTypeCreateModel("Test", "test");
         var result = await ContentTypeEditingService.CreateAsync(createModel, Constants.Security.SuperUserKey);
         Assert.IsTrue(result.Success);
 
-        createModel = ContentTypeCreateModel("Test 2", "test");
+        createModel = ContentTypeCreateModel("Test 2", newAlias);
         result = await ContentTypeEditingService.CreateAsync(createModel, Constants.Security.SuperUserKey);
         Assert.IsFalse(result.Success);
         Assert.AreEqual(ContentTypeOperationStatus.DuplicateAlias, result.Status);