diff --git a/libs/panners/1in2out/panner_1in2out.cc b/libs/panners/1in2out/panner_1in2out.cc
index 3dc3b53e2c..753c3a2dae 100644
--- a/libs/panners/1in2out/panner_1in2out.cc
+++ b/libs/panners/1in2out/panner_1in2out.cc
@@ -336,9 +336,9 @@ XMLNode&
 Panner1in2out::get_state ()
 {
 	XMLNode& root (Panner::get_state ());
-	root.add_property (X_("uri"), _descriptor.panner_uri);
+	root.set_property (X_("uri"), _descriptor.panner_uri);
 	/* this is needed to allow new sessions to load with old Ardour: */
-	root.add_property (X_("type"), _descriptor.name);
+	root.set_property (X_("type"), _descriptor.name);
 	return root;
 }
 
diff --git a/libs/panners/2in2out/panner_2in2out.cc b/libs/panners/2in2out/panner_2in2out.cc
index 9105eff713..2b14f6458c 100644
--- a/libs/panners/2in2out/panner_2in2out.cc
+++ b/libs/panners/2in2out/panner_2in2out.cc
@@ -479,9 +479,9 @@ XMLNode&
 Panner2in2out::get_state ()
 {
 	XMLNode& root (Panner::get_state ());
-	root.add_property (X_("uri"), _descriptor.panner_uri);
+	root.set_property (X_("uri"), _descriptor.panner_uri);
 	/* this is needed to allow new sessions to load with old Ardour: */
-	root.add_property (X_("type"), _descriptor.name);
+	root.set_property (X_("type"), _descriptor.name);
 	return root;
 }
 
diff --git a/libs/panners/stereobalance/panner_balance.cc b/libs/panners/stereobalance/panner_balance.cc
index 647c92ada3..f7379f9d6d 100644
--- a/libs/panners/stereobalance/panner_balance.cc
+++ b/libs/panners/stereobalance/panner_balance.cc
@@ -270,9 +270,9 @@ Pannerbalance::factory (boost::shared_ptr<Pannable> p, boost::shared_ptr<Speaker
 Pannerbalance::get_state ()
 {
 	XMLNode& root (Panner::get_state ());
-	root.add_property (X_("uri"), _descriptor.panner_uri);
+	root.set_property (X_("uri"), _descriptor.panner_uri);
 	/* this is needed to allow new sessions to load with old Ardour: */
-	root.add_property (X_("type"), _descriptor.name);
+	root.set_property (X_("type"), _descriptor.name);
 	return root;
 }
 
diff --git a/libs/panners/vbap/vbap.cc b/libs/panners/vbap/vbap.cc
index e6cbd3655f..aba9641cb5 100644
--- a/libs/panners/vbap/vbap.cc
+++ b/libs/panners/vbap/vbap.cc
@@ -366,9 +366,9 @@ XMLNode&
 VBAPanner::get_state ()
 {
 	XMLNode& node (Panner::get_state());
-	node.add_property (X_("uri"), _descriptor.panner_uri);
+	node.set_property (X_("uri"), _descriptor.panner_uri);
 	/* this is needed to allow new sessions to load with old Ardour: */
-	node.add_property (X_("type"), _descriptor.name);
+	node.set_property (X_("type"), _descriptor.name);
 	return node;
 }