diff --git a/docs/reference/gtk/gtk3-sections.txt b/docs/reference/gtk/gtk3-sections.txt
index beb2090ff6..b6a47ac9a5 100644
--- a/docs/reference/gtk/gtk3-sections.txt
+++ b/docs/reference/gtk/gtk3-sections.txt
@@ -5678,6 +5678,7 @@ GTK_STYLE_CLASS_LEFT
 GTK_STYLE_CLASS_RIGHT
 GTK_STYLE_CLASS_LINKED
 GTK_STYLE_CLASS_ARROW
+GTK_STYLE_CLASS_OSD
 GTK_STYLE_REGION_COLUMN
 GTK_STYLE_REGION_COLUMN_HEADER
 GTK_STYLE_REGION_ROW
diff --git a/gtk/gtkstylecontext.h b/gtk/gtkstylecontext.h
index ff1e7f57cf..1a1f73ee19 100644
--- a/gtk/gtkstylecontext.h
+++ b/gtk/gtkstylecontext.h
@@ -673,6 +673,14 @@ struct _GtkStyleContextClass
  */
 #define GTK_STYLE_CLASS_ARROW "arrow"
 
+/**
+ * GTK_STYLE_CLASS_OSD:
+ *
+ * A CSS class used when rendering an OSD (On Screen Display) element,
+ * on top of another container.
+ */
+#define GTK_STYLE_CLASS_OSD "osd"
+
 /* Predefined set of widget regions */
 
 /**