diff --git a/docs/reference/gtk/gtk3-sections.txt b/docs/reference/gtk/gtk3-sections.txt
index cdcad3f662..5126e896e3 100644
--- a/docs/reference/gtk/gtk3-sections.txt
+++ b/docs/reference/gtk/gtk3-sections.txt
@@ -5633,6 +5633,7 @@ GTK_STYLE_CLASS_MENU
 GTK_STYLE_CLASS_RADIO
 GTK_STYLE_CLASS_RUBBERBAND
 GTK_STYLE_CLASS_SCROLLBAR
+GTK_STYLE_CLASS_SCROLLBARS_JUNCTION
 GTK_STYLE_CLASS_SLIDER
 GTK_STYLE_CLASS_TOOLTIP
 GTK_STYLE_CLASS_TROUGH
diff --git a/gtk/gtkstylecontext.h b/gtk/gtkstylecontext.h
index 16a8c05d29..dc528ef8dc 100644
--- a/gtk/gtkstylecontext.h
+++ b/gtk/gtkstylecontext.h
@@ -332,6 +332,16 @@ struct _GtkStyleContextClass
  */
 #define GTK_STYLE_CLASS_SCROLLBAR "scrollbar"
 
+/**
+ * GTK_STYLE_CLASS_SCROLLBARS_JUNCTION:
+ *
+ * A CSS class to match the junction area between an horizontal
+ * and vertical scrollbar, when they're both shown.
+ * 
+ * This is used in #GtkScrolledWindow.
+ */
+#define GTK_STYLE_CLASS_SCROLLBARS_JUNCTION "scrollbars-junction"
+
 /**
  * GTK_STYLE_CLASS_SCALE:
  *