diff --git a/src/beast/beast/threads/ServiceQueue.h b/src/beast/beast/threads/ServiceQueue.h
index 715b6c52f..2b2cb3bea 100644
--- a/src/beast/beast/threads/ServiceQueue.h
+++ b/src/beast/beast/threads/ServiceQueue.h
@@ -351,7 +351,7 @@ protected:
     class ScopedServiceThread;
 
     void wait();
-    void enqueue (Item* item);
+    virtual void enqueue (Item* item);
 
     virtual std::size_t dequeue() = 0;
     virtual Waiter* new_waiter() = 0;