diff --git a/clutter/clutter/clutter-constraint-private.h b/clutter/clutter/clutter-constraint-private.h
index 2bed47be2..5fbddef00 100644
--- a/clutter/clutter/clutter-constraint-private.h
+++ b/clutter/clutter/clutter-constraint-private.h
@@ -30,13 +30,6 @@ gboolean clutter_constraint_update_allocation (ClutterConstraint *constraint,
                                                ClutterActor      *actor,
                                                ClutterActorBox   *allocation);
 
-void clutter_constraint_update_preferred_size (ClutterConstraint  *constraint,
-                                               ClutterActor       *actor,
-                                               ClutterOrientation  direction,
-                                               float               for_size,
-                                               float              *minimum_size,
-                                               float              *natural_size);
-
 G_END_DECLS
 
 #endif /* __CLUTTER_CONSTRAINT_PRIVATE_H__ */
diff --git a/clutter/clutter/clutter-constraint.c b/clutter/clutter/clutter-constraint.c
index 960280009..b575fc63d 100644
--- a/clutter/clutter/clutter-constraint.c
+++ b/clutter/clutter/clutter-constraint.c
@@ -222,6 +222,17 @@ clutter_constraint_update_allocation (ClutterConstraint *constraint,
   return !clutter_actor_box_equal (allocation, &old_alloc);
 }
 
+/**
+ * clutter_constraint_update_preferred_size:
+ * @constraint: a #ClutterConstraint
+ * @actor: a #ClutterActor
+ * @direction: a #ClutterOrientation
+ * @for_size: the size in the opposite direction
+ * @minimum_size: (inout): the minimum size to modify
+ * @natural_size: (inout): the natural size to modify
+ *
+ * Asks the @constraint to update the size request of a #ClutterActor.
+ */
 void
 clutter_constraint_update_preferred_size (ClutterConstraint  *constraint,
                                           ClutterActor       *actor,
diff --git a/clutter/clutter/clutter-constraint.h b/clutter/clutter/clutter-constraint.h
index f2ecd506a..420e7de75 100644
--- a/clutter/clutter/clutter-constraint.h
+++ b/clutter/clutter/clutter-constraint.h
@@ -99,6 +99,14 @@ struct _ClutterConstraintClass
 CLUTTER_EXPORT
 GType clutter_constraint_get_type (void) G_GNUC_CONST;
 
+CLUTTER_EXPORT
+void clutter_constraint_update_preferred_size (ClutterConstraint  *constraint,
+                                               ClutterActor       *actor,
+                                               ClutterOrientation  direction,
+                                               float               for_size,
+                                               float              *minimum_size,
+                                               float              *natural_size);
+
 /* ClutterActor API */
 CLUTTER_EXPORT
 void               clutter_actor_add_constraint            (ClutterActor      *self,