diff --git a/README.md b/README.md
index 1cd8069..ea360bb 100644
--- a/README.md
+++ b/README.md
@@ -3,8 +3,6 @@
        align="right" width="64" height="64" />
 </h2>
 
-**2024-01-19**: Seems to be b0rked w/ Xcode 15.2: Issue https://github.com/Data-swift/ManagedModels/issues/25
-
 > Instead of wrapping CoreData, use it directly :-)
 
 The key thing **ManagedModels** provides is a `@Model` macro, 
diff --git a/Sources/ManagedModels/SchemaCompatibility/NSAttributeDescription+Data.swift b/Sources/ManagedModels/SchemaCompatibility/NSAttributeDescription+Data.swift
index 141ad3a..66672c9 100644
--- a/Sources/ManagedModels/SchemaCompatibility/NSAttributeDescription+Data.swift
+++ b/Sources/ManagedModels/SchemaCompatibility/NSAttributeDescription+Data.swift
@@ -84,9 +84,12 @@ extension CoreData.NSAttributeDescription: SchemaProperty {
             ValueTransformer
               .setValueTransformer(transformer, forName: .init(name))
           }
+          assert(ValueTransformer.valueTransformerNames().contains(.init(name)))
           valueTransformerName = name
+          assert(valueTransformerName != nil)
         }
         setValueClassName(for: codableType)
+        return
       }
 
       // TBD:
@@ -162,7 +165,11 @@ public extension NSAttributeDescription {
     if let hashModifier { versionHashModifier = hashModifier }
     if let defaultValue { self.defaultValue   = defaultValue }
     isOptional = valueType is any AnyOptional.Type
+    
+    assert(valueTransformerName == nil)
+    valueTransformerName = nil
     if valueType != Any.self { self.valueType = valueType }
+    
     setOptions(options)
   }
 }
@@ -174,7 +181,6 @@ private extension NSAttributeDescription {
     allowsExternalBinaryDataStorage   = false
     isIndexedBySpotlight              = false
     isTransient                       = false
-    valueTransformerName              = nil
     if #available(iOS 15.0, macOS 12.0, tvOS 15.0, watchOS 8.0, *) {
       allowsCloudEncryption = false
     }
@@ -190,8 +196,10 @@ private extension NSAttributeDescription {
         case .ephemeral: isTransient = true
 
         case .transformableByName(let name):
+          assert(valueTransformerName == nil)
           valueTransformerName = name
         case .transformableByType(let type):
+          assert(valueTransformerName == nil)
           valueTransformerName = NSStringFromClass(type)
 
         case .allowsCloudEncryption: // FIXME: restrict availability
diff --git a/Tests/ManagedModelTests/CodablePropertiesTest.swift b/Tests/ManagedModelTests/CodablePropertiesTest.swift
new file mode 100644
index 0000000..7639fef
--- /dev/null
+++ b/Tests/ManagedModelTests/CodablePropertiesTest.swift
@@ -0,0 +1,71 @@
+//
+//  Created by Helge Heß.
+//  Copyright © 2024 ZeeZide GmbH.
+//
+
+import XCTest
+import Foundation
+import CoreData
+@testable import ManagedModels
+
+final class CodablePropertiesTests: XCTestCase {
+
+  private lazy var container = try? ModelContainer(
+    for: Fixtures.CodablePropertiesSchema.managedObjectModel,
+    configurations: ModelConfiguration(isStoredInMemoryOnly: true)
+  )
+  
+  func testEntityName() throws {
+    let entityType = Fixtures.CodablePropertiesSchema.StoredAccess.self
+    XCTAssertEqual(entityType.entity().name, "StoredAccess")
+  }
+  
+  func testPropertySetup() throws {
+    let valueType = Fixtures.CodablePropertiesSchema.AccessSIP.self
+    let attribute = CoreData.NSAttributeDescription(
+      name: "sip",
+      valueType: valueType,
+      defaultValue: nil
+    )
+    XCTAssertEqual(attribute.name, "sip")
+    XCTAssertEqual(attribute.attributeType, .transformableAttributeType)
+
+    let transformerName = try XCTUnwrap(
+      ValueTransformer.valueTransformerNames().first(where: {
+        $0.rawValue.range(of: "CodableBox11TransformerVOO17ManagedModelTests8")
+        != nil
+      })
+    )
+    let transformer = try XCTUnwrap(ValueTransformer(forName: transformerName))
+    _ = transformer // to clear unused-wraning
+
+    XCTAssertTrue(attribute.valueType ==
+                  CodableBox<Fixtures.CodablePropertiesSchema.AccessSIP>.self)
+    XCTAssertNotNil(attribute.valueTransformerName)
+    XCTAssertEqual(attribute.valueTransformerName, transformerName.rawValue)
+  }
+  
+  func testCodablePropertyEntity() throws {
+    let entity = try XCTUnwrap(
+      container?.managedObjectModel.entitiesByName["StoredAccess"]
+    )
+
+    // Creating the entity should have registered the transformer for the
+    // CodableBox.
+    let transformerName = try XCTUnwrap(
+      ValueTransformer.valueTransformerNames().first(where: {
+        $0.rawValue.range(of: "CodableBox11TransformerVOO17ManagedModelTests8")
+        != nil
+      })
+    )
+    let transformer = try XCTUnwrap(ValueTransformer(forName: transformerName))
+    _ = transformer // to clear unused-wraning
+
+    let attribute = try XCTUnwrap(entity.attributesByName["sip"])
+    XCTAssertEqual(attribute.name, "sip")
+    XCTAssertTrue(attribute.valueType == 
+                  CodableBox<Fixtures.CodablePropertiesSchema.AccessSIP>.self)
+    XCTAssertNotNil(attribute.valueTransformerName)
+    XCTAssertEqual(attribute.valueTransformerName, transformerName.rawValue)
+  }
+}
diff --git a/Tests/ManagedModelTests/Schemas/CodablePropertySchema.swift b/Tests/ManagedModelTests/Schemas/CodablePropertySchema.swift
new file mode 100644
index 0000000..2482789
--- /dev/null
+++ b/Tests/ManagedModelTests/Schemas/CodablePropertySchema.swift
@@ -0,0 +1,31 @@
+//
+//  Created by Helge Heß.
+//  Copyright © 2024 ZeeZide GmbH.
+//
+
+import ManagedModels
+
+extension Fixtures {
+  // https://github.com/Data-swift/ManagedModels/issues/27
+  
+  enum CodablePropertiesSchema: VersionedSchema {
+    static var models : [ any PersistentModel.Type ] = [
+      StoredAccess.self
+    ]
+    
+    public static let versionIdentifier = Schema.Version(0, 1, 0)
+
+    @Model
+    final class StoredAccess: NSManagedObject {
+      var token   : String
+      var expires : Date
+      var sip     : AccessSIP
+    }
+    
+    struct AccessSIP: Codable {
+      var username : String
+      var password : String
+      var realm    : String
+    }
+  }
+}