diff --git a/Split/Api/SplitDatabaseHelper.swift b/Split/Api/SplitDatabaseHelper.swift
index 3382e24b..f1832437 100644
--- a/Split/Api/SplitDatabaseHelper.swift
+++ b/Split/Api/SplitDatabaseHelper.swift
@@ -17,7 +17,12 @@ struct SplitDatabaseHelper {
     /// This avoids issues in concurrent initialization of SDK instances using the same SDK key + prefix,
     /// while still allowing different dbKeys to initialize in parallel.
     static private let storageLockMapGuard = NSLock()
+    
+    #if swift(>=6.0)
     nonisolated(unsafe) static private var storageLockMap: [String: NSLock] = [:]
+    #else
+    static private var storageLockMap: [String: NSLock] = [:]
+    #endif
     
     static private func storageLock(for dbKey: String) -> NSLock {
         storageLockMapGuard.lock()