diff --git a/libs/ardour/ardour/lv2_extensions.h b/libs/ardour/ardour/lv2_extensions.h
index f38ac8122a..ebdf905fb3 100644
--- a/libs/ardour/ardour/lv2_extensions.h
+++ b/libs/ardour/ardour/lv2_extensions.h
@@ -194,16 +194,26 @@ typedef struct {
 } LV2_Midnam;
 
 typedef struct {
-	/** query midnam document. The plugin
-	 * is expected to return an allocated
-	 * null-terminated XML text, which is
-	 * safe for the host to pass to free().
+	/** Query midnam document. The plugin
+	 * is expected to return a null-terminated XML
+	 * text which is a valid midnam desciption
+	 * (or NULL in case of error).
 	 *
 	 * The midnam <Model> must be unique and
 	 * specific for the given plugin-instance.
 	 */
 	char* (*midnam)(LV2_Handle instance);
+
+	/** The unique model id used ith the midnam,
+	 * (or NULL).
+	 */
 	char* (*model)(LV2_Handle instance);
+
+	/** free allocated strings. The host
+	 * calls this for every value returned by
+	 * \ref midnam and \ref model.
+	 */
+	void (*free)(char*);
 } LV2_Midnam_Interface;
 
 /**
diff --git a/libs/ardour/lv2_plugin.cc b/libs/ardour/lv2_plugin.cc
index 0892d86c33..94760dc336 100644
--- a/libs/ardour/lv2_plugin.cc
+++ b/libs/ardour/lv2_plugin.cc
@@ -985,7 +985,7 @@ LV2Plugin::read_midnam () {
 		MIDI::Name::MidiPatchManager::instance().remove_custom_midnam (ss.str());
 		rv = MIDI::Name::MidiPatchManager::instance().add_custom_midnam (ss.str(), midnam);
 	}
-	free (midnam);
+	_midname_interface->free (midnam);
 	return rv;
 }
 
@@ -999,7 +999,7 @@ LV2Plugin::midnam_model () {
 	if (model) {
 		rv = model;
 	}
-	free (model);
+	_midname_interface->free (model);
 	return rv;
 }
 #endif