diff --git a/Runtime/CToken.hpp b/Runtime/CToken.hpp
index 906786aa1..699f3c1ec 100644
--- a/Runtime/CToken.hpp
+++ b/Runtime/CToken.hpp
@@ -74,7 +74,7 @@ class CToken {
 
 public:
   /* Added to test for non-null state */
-  operator bool() const { return x0_objRef != nullptr; }
+  explicit operator bool() const { return x0_objRef != nullptr; }
   void Unlock();
   void Lock();
   bool IsLocked() const { return x4_lockHeld; }