diff --git a/policy_manager/variable.h b/policy_manager/variable.h
index 79953ed..22039c0 100644
--- a/policy_manager/variable.h
+++ b/policy_manager/variable.h
@@ -12,7 +12,8 @@
 
 namespace chromeos_policy_manager {
 
-// Interface to a Policy Manager variable to be implemented by the providers.
+// Interface to a Policy Manager variable. Implementation internals are hidden
+// as protected members, since policies should not be using them directly.
 template<typename T>
 class Variable {
  public: