diff --git a/IB/Shared/shared_ptr.h b/IB/Shared/shared_ptr.h
index c29f3aa..4c6403d 100644
--- a/IB/Shared/shared_ptr.h
+++ b/IB/Shared/shared_ptr.h
@@ -74,6 +74,7 @@ public:
 
    X& operator*()  const { return *ptr_; }
    X* operator->() const { return ptr_; }
+   operator bool() const { return ptr_ != 0; }
    X* get()        const { return ptr_; }
    bool only() const { return use_.only(); }
 
