diff --git a/gtk/gtkwidget.c b/gtk/gtkwidget.c
index e44e60341f..b3b0a3bd8e 100644
--- a/gtk/gtkwidget.c
+++ b/gtk/gtkwidget.c
@@ -10114,6 +10114,20 @@ _gtk_widget_scale_changed (GtkWidget *widget)
                           NULL);
 }
 
+/**
+ * gtk_widget_get_scale_factor:
+ * @widget: a #GtkWidget
+ *
+ * Retrieves the internal scale factor that maps from window coordinates
+ * to the actual device pixels. On traditional systems this is 1, on
+ * high density outputs, it can be a higher value (typically 2).
+ *
+ * See gdk_window_get_scale_factor().
+ *
+ * Returns: the scale factor for @widget
+ *
+ * Since: 3.10
+ */
 gint
 gtk_widget_get_scale_factor (GtkWidget *widget)
 {