diff --git a/drmproperty.h b/drmproperty.h
index 5e358be..f1328fe 100644
--- a/drmproperty.h
+++ b/drmproperty.h
@@ -46,6 +46,7 @@
   std::string name() const;
 
   int value(uint64_t *value) const;
+  bool immutable() const;
 
  private:
   class DrmPropertyEnum {