diff --git a/gtk/gtkconstraintguide.c b/gtk/gtkconstraintguide.c
index f6fcd8d546..512b91cfd4 100644
--- a/gtk/gtkconstraintguide.c
+++ b/gtk/gtkconstraintguide.c
@@ -500,8 +500,8 @@ gtk_constraint_guide_set_min_size (GtkConstraintGuide *guide,
 /**
  * gtk_constraint_guide_get_min_size:
  * @guide: a `GtkConstraintGuide` object
- * @width: (nullable): return location for the minimum width
- * @height: (nullable): return location for the minimum height
+ * @width: (out) (optional): return location for the minimum width
+ * @height: (out) (optional): return location for the minimum height
  *
  * Gets the minimum size of @guide.
  */
@@ -552,8 +552,8 @@ gtk_constraint_guide_set_nat_size (GtkConstraintGuide *guide,
 /**
  * gtk_constraint_guide_get_nat_size:
  * @guide: a `GtkConstraintGuide` object
- * @width: (nullable): return location for the natural width
- * @height: (nullable): return location for the natural height
+ * @width: (out) (optional): return location for the natural width
+ * @height: (out) (optional): return location for the natural height
  *
  * Gets the natural size of @guide.
  */
@@ -604,8 +604,8 @@ gtk_constraint_guide_set_max_size (GtkConstraintGuide *guide,
 /**
  * gtk_constraint_guide_get_max_size:
  * @guide: a `GtkConstraintGuide` object
- * @width: (nullable): return location for the maximum width
- * @height: (nullable): return location for the maximum height
+ * @width: (out) (optional): return location for the maximum width
+ * @height: (out) (optional): return location for the maximum height
  *
  * Gets the maximum size of @guide.
  */