diff --git a/gtk/gtkstylecontext.h b/gtk/gtkstylecontext.h
index daf997fa08..e687ff13e4 100644
--- a/gtk/gtkstylecontext.h
+++ b/gtk/gtkstylecontext.h
@@ -393,6 +393,13 @@ struct _GtkStyleContextClass
  */
 #define GTK_STYLE_CLASS_VIEW "view"
 
+/**
+ * GTK_STYLE_CLASS_SIDEBAR:
+ *
+ * A widget class defining a sidebar
+ */
+#define GTK_STYLE_CLASS_SIDEBAR "sidebar"
+
 /**
  * GTK_STYLE_CLASS_HIGHLIGHT:
  *