diff --git a/gtk/gtkexpression.c b/gtk/gtkexpression.c
index eba1a868b0..9839e262a5 100644
--- a/gtk/gtkexpression.c
+++ b/gtk/gtkexpression.c
@@ -127,8 +127,9 @@
  *
  * To create a property expression, use the `<lookup>` element. It can have a `type`
  * attribute to specify the object type, and a `name` attribute to specify the property
- * to look up. The content of `<lookup>` can either be an element specifying the expression
- * to use the object, or a string that specifies the name of the object to use.
+ * to look up. The content of `<lookup>` can either be a string that specifies the name
+ * of the object to use, an element specifying an expression to provide an object, or
+ * empty to use the `this` object.
  *
  * Example:
  *