diff --git a/Sources/SQLiteData/CloudKit/SyncEngine.swift b/Sources/SQLiteData/CloudKit/SyncEngine.swift
index ddcb3f32..93d74960 100644
--- a/Sources/SQLiteData/CloudKit/SyncEngine.swift
+++ b/Sources/SQLiteData/CloudKit/SyncEngine.swift
@@ -34,7 +34,11 @@
     let foreignKeysByTableName: [String: [ForeignKey]]
     package let syncEngines = LockIsolated<SyncEngines>(SyncEngines())
     package let defaultZone: CKRecordZone
-    let delegate: (any SyncEngineDelegate)?
+    #if compiler(<6.2.3)
+      weak var delegate: (any SyncEngineDelegate)?
+    #else
+      weak let delegate: (any SyncEngineDelegate)?
+    #endif
     let defaultSyncEngines:
       @Sendable (any DatabaseReader, SyncEngine)
         -> (private: any SyncEngineProtocol, shared: any SyncEngineProtocol)
@@ -945,6 +949,14 @@
     }
   }
 
+  #if compiler(<6.2.3)
+    @available(iOS 17, macOS 14, tvOS 17, watchOS 10, *)
+    extension SyncEngine: @unchecked Sendable {}
+  #else
+    @available(iOS 17, macOS 14, tvOS 17, watchOS 10, *)
+    extension SyncEngine: Sendable {}
+  #endif
+
   extension PrimaryKeyedTable {
     @available(iOS 17, macOS 14, tvOS 17, watchOS 10, *)
     fileprivate static func createTriggers(
diff --git a/Tests/SQLiteDataTests/CloudKitTests/SyncEngineDelegateTests.swift b/Tests/SQLiteDataTests/CloudKitTests/SyncEngineDelegateTests.swift
index 395be01e..c8e410e9 100644
--- a/Tests/SQLiteDataTests/CloudKitTests/SyncEngineDelegateTests.swift
+++ b/Tests/SQLiteDataTests/CloudKitTests/SyncEngineDelegateTests.swift
@@ -15,7 +15,6 @@
     @MainActor
     final class SyncEngineDelegateTests: BaseCloudKitTests, @unchecked Sendable {
       @available(iOS 17, macOS 14, tvOS 17, watchOS 10, *)
-
       @Test($syncEngineDelegate.set(MyDelegate()))
       func accountChanged() async throws {
         try await userDatabase.userWrite { db in