diff --git a/beast/module/core/thread/Workers.h b/beast/module/core/thread/Workers.h
index 0fb8daf155..0f54ca3e00 100644
--- a/beast/module/core/thread/Workers.h
+++ b/beast/module/core/thread/Workers.h
@@ -56,7 +56,8 @@ public:
     */
     explicit Workers (Callback& callback,
                       String const& threadNames = "Worker",
-                      int numberOfThreads = std::thread::hardware_concurrency());
+                      int numberOfThreads =
+                         static_cast<int>(std::thread::hardware_concurrency()));
 
     ~Workers ();