diff --git a/uSync.Core/Serialization/Serializers/MediaSerializer.cs b/uSync.Core/Serialization/Serializers/MediaSerializer.cs
index 43353cef..9b9fe8c1 100644
--- a/uSync.Core/Serialization/Serializers/MediaSerializer.cs
+++ b/uSync.Core/Serialization/Serializers/MediaSerializer.cs
@@ -198,7 +198,7 @@ private static string GetFilePath(string? value)
             }
             catch (Exception ex)
             {
-                logger.LogError(ex, "Error creating media item with alias {alias} and parent {parentId}", alias, parentId);
+                logger.LogError(ex, "Error creating media item with alias {alias} and parent {parentId}", alias, parent?.Id);
                 throw;
             }
 
diff --git a/uSync.Tests/Migrations/NestedContentMigrationTests.cs b/uSync.Tests/Migrations/NestedContentMigrationTests.cs
new file mode 100644
index 00000000..758dca5e
--- /dev/null
+++ b/uSync.Tests/Migrations/NestedContentMigrationTests.cs
@@ -0,0 +1,204 @@
+using System;
+
+using Moq;
+
+using NUnit.Framework;
+
+using Umbraco.Cms.Core.Models;
+using Umbraco.Cms.Core.Services;
+
+using uSync.Core.DataTypes.DataTypeSerializers;
+
+namespace uSync.Tests.Migrations;
+
+[TestFixture]
+internal class NestedContentMigrationTests : MigrationTestBase
+{
+    private NestedContentMigratingConfig _serializer;
+    private Mock<IContentTypeService> _mockContentTypeService;
+
+    [SetUp]
+    public void Setup()
+    {
+        _mockContentTypeService = new Mock<IContentTypeService>();
+
+        var articleContentType = new Mock<IContentType>();
+        articleContentType.Setup(x => x.Key).Returns(Guid.Parse("cc07b313-0843-4aa8-bbda-871c8da728c8"));
+
+        var blogContentType = new Mock<IContentType>();
+        blogContentType.Setup(x => x.Key).Returns(Guid.Parse("4c52d8ab-54e6-40cd-999c-7a5f24903e4d"));
+
+        _mockContentTypeService.Setup(x => x.Get("articleType")).Returns(articleContentType.Object);
+        _mockContentTypeService.Setup(x => x.Get("blogType")).Returns(blogContentType.Object);
+
+        _serializer = new NestedContentMigratingConfig(_mockContentTypeService.Object);
+    }
+
+    private static readonly string FullMigrationSource = @"{
+  ""minItems"": 1,
+  ""maxItems"": 5,
+  ""contentTypes"": [
+    { ""ncAlias"": ""articleType"" },
+    { ""ncAlias"": ""blogType"" }
+  ]
+}";
+
+    private static readonly string FullMigrationTarget = @"{
+  ""blocks"": [
+    {
+      ""contentElementTypeKey"": ""cc07b313-0843-4aa8-bbda-871c8da728c8"",
+      ""settingsElementTypeKey"": null
+    },
+    {
+      ""contentElementTypeKey"": ""4c52d8ab-54e6-40cd-999c-7a5f24903e4d"",
+      ""settingsElementTypeKey"": null
+    }
+  ],
+  ""useSingleBlockMode"": false,
+  ""validationLimit"": {
+    ""max"": 5,
+    ""min"": 1
+  }
+}";
+
+    [Test]
+    public void FullMigrationTest()
+        => TestSerializerPropertyMigration(_serializer, FullMigrationSource, FullMigrationTarget);
+
+    private static readonly string MinOnlySource = @"{
+  ""minItems"": 2,
+  ""contentTypes"": [
+    { ""ncAlias"": ""articleType"" }
+  ]
+}";
+
+    private static readonly string MinOnlyTarget = @"{
+  ""blocks"": [
+    {
+      ""contentElementTypeKey"": ""cc07b313-0843-4aa8-bbda-871c8da728c8"",
+      ""settingsElementTypeKey"": null
+    }
+  ],
+  ""useSingleBlockMode"": false,
+  ""validationLimit"": {
+    ""max"": null,
+    ""min"": 2
+  }
+}";
+
+    [Test]
+    public void MinOnlyMigrationTest()
+        => TestSerializerPropertyMigration(_serializer, MinOnlySource, MinOnlyTarget);
+
+    private static readonly string MaxOnlySource = @"{
+  ""maxItems"": 3,
+  ""contentTypes"": [
+    { ""ncAlias"": ""blogType"" }
+  ]
+}";
+
+    private static readonly string MaxOnlyTarget = @"{
+  ""blocks"": [
+    {
+      ""contentElementTypeKey"": ""4c52d8ab-54e6-40cd-999c-7a5f24903e4d"",
+      ""settingsElementTypeKey"": null
+    }
+  ],
+  ""useSingleBlockMode"": false,
+  ""validationLimit"": {
+    ""max"": 3,
+    ""min"": null
+  }
+}";
+
+    [Test]
+    public void MaxOnlyMigrationTest()
+        => TestSerializerPropertyMigration(_serializer, MaxOnlySource, MaxOnlyTarget);
+
+    private static readonly string NoValidationLimitsSource = @"{
+  ""contentTypes"": [
+    { ""ncAlias"": ""articleType"" }
+  ]
+}";
+
+    private static readonly string NoValidationLimitsTarget = @"{
+  ""blocks"": [
+    {
+      ""contentElementTypeKey"": ""cc07b313-0843-4aa8-bbda-871c8da728c8"",
+      ""settingsElementTypeKey"": null
+    }
+  ],
+  ""useSingleBlockMode"": false,
+  ""validationLimit"": {
+    ""max"": null,
+    ""min"": null
+  }
+}";
+
+    [Test]
+    public void NoValidationLimitsMigrationTest()
+        => TestSerializerPropertyMigration(_serializer, NoValidationLimitsSource, NoValidationLimitsTarget);
+
+    private static readonly string UnknownAliasSource = @"{
+  ""contentTypes"": [
+    { ""ncAlias"": ""unknownType"" }
+  ]
+}";
+
+    private static readonly string UnknownAliasTarget = @"{
+  ""blocks"": null,
+  ""useSingleBlockMode"": false,
+  ""validationLimit"": {
+    ""max"": null,
+    ""min"": null
+  }
+}";
+
+    [Test]
+    public void UnknownAliasIsSkippedTest()
+        => TestSerializerPropertyMigration(_serializer, UnknownAliasSource, UnknownAliasTarget);
+
+    private static readonly string MixedAliasesSource = @"{
+  ""contentTypes"": [
+    { ""ncAlias"": ""articleType"" },
+    { ""ncAlias"": ""unknownType"" }
+  ]
+}";
+
+    private static readonly string MixedAliasesTarget = @"{
+  ""blocks"": [
+    {
+      ""contentElementTypeKey"": ""cc07b313-0843-4aa8-bbda-871c8da728c8"",
+      ""settingsElementTypeKey"": null
+    }
+  ],
+  ""useSingleBlockMode"": false,
+  ""validationLimit"": {
+    ""max"": null,
+    ""min"": null
+  }
+}";
+
+    [Test]
+    public void UnknownAliasInMixedListIsSkippedTest()
+        => TestSerializerPropertyMigration(_serializer, MixedAliasesSource, MixedAliasesTarget);
+
+    private static readonly string EmptyContentTypesSource = @"{
+  ""minItems"": 1,
+  ""maxItems"": 2,
+  ""contentTypes"": []
+}";
+
+    private static readonly string EmptyContentTypesTarget = @"{
+  ""blocks"": null,
+  ""useSingleBlockMode"": false,
+  ""validationLimit"": {
+    ""max"": 2,
+    ""min"": 1
+  }
+}";
+
+    [Test]
+    public void EmptyContentTypesMigrationTest()
+        => TestSerializerPropertyMigration(_serializer, EmptyContentTypesSource, EmptyContentTypesTarget);
+}
diff --git a/uSync.Tests/appsettings-schema.Umbraco.Cms.json b/uSync.Tests/appsettings-schema.Umbraco.Cms.json
old mode 100644
new mode 100755
diff --git a/uSync.Tests/umbraco-package-schema.json b/uSync.Tests/umbraco-package-schema.json
old mode 100644
new mode 100755