diff --git a/simgear/props/props.cxx b/simgear/props/props.cxx
index 9d941559..c6a84df0 100644
--- a/simgear/props/props.cxx
+++ b/simgear/props/props.cxx
@@ -849,7 +849,7 @@ SGPropertyNode::trace_read () const
  * Last used attribute
  * Update as needed when enum Attribute is changed
  */
-const int SGPropertyNode::LAST_USED_ATTRIBUTE = PROTECTED;
+const int SGPropertyNode::LAST_USED_ATTRIBUTE = LISTENER_SAFE;
 
 /**
  * Default constructor: always creates a root node.
diff --git a/simgear/props/props.hxx b/simgear/props/props.hxx
index 3afc8796..0d407c99 100644
--- a/simgear/props/props.hxx
+++ b/simgear/props/props.hxx
@@ -821,6 +821,7 @@ public:
     USERARCHIVE = 64,
     PRESERVE = 128,
     PROTECTED   = 1 << 8,
+    LISTENER_SAFE = 1 << 9, /// it's safe to listen to this property, even if it's tied
     // beware: if you add another attribute here,
     // also update value of "LAST_USED_ATTRIBUTE".
   };