diff --git a/gtk/gtkstack.c b/gtk/gtkstack.c
index 56dc3cfafb..ce5486ccd7 100644
--- a/gtk/gtkstack.c
+++ b/gtk/gtkstack.c
@@ -1646,6 +1646,7 @@ gtk_stack_get_transition_running (GtkStack *stack)
 /**
  * gtk_stack_set_interpolate_size:
  * @stack: A #GtkStack
+ * @interpole_size: the new value
  *
  * Sets whether or not @stack will interpolate its size when
  * changing the visible child. If the interpolate-size property