diff --git a/src/matrix-api.c b/src/matrix-api.c
index 85254b1..1fd0189 100644
--- a/src/matrix-api.c
+++ b/src/matrix-api.c
@@ -2092,7 +2092,7 @@ matrix_api_delete_room_tag(MatrixAPI *api,
  * @user_id: the ID of the user to add the tag for
  * @room_id: the ID of the room to add the tag for
  * @tag: the tag to add
- * @content: extra data for the tag, e.g. ordering
+ * @content: (transfer full): extra data for the tag, e.g. ordering
  * @error: return location for a #GError, or %NULL
  *
  * Add a tag to the room.
diff --git a/src/matrix-api.h b/src/matrix-api.h
index d367eac..22bd1c2 100644
--- a/src/matrix-api.h
+++ b/src/matrix-api.h
@@ -456,7 +456,7 @@ struct _MatrixAPIInterface {
                          const gchar *user_id,
                          const gchar *room_id,
                          const gchar *tag,
-                         const JsonNode *content,
+                         JsonNode *content,
                          GError **error);
 
     /* VoIP */