diff --git a/src/hb-ot-layout-common-private.hh b/src/hb-ot-layout-common-private.hh
index 40a435e..5faedcc 100644
--- a/src/hb-ot-layout-common-private.hh
+++ b/src/hb-ot-layout-common-private.hh
@@ -32,6 +32,11 @@
 #include "hb-open-type-private.hh"
 
 
+#define NO_CONTEXT		((unsigned int) 0x110000)
+#define NOT_COVERED		((unsigned int) 0x110000)
+#define MAX_NESTING_LEVEL	8
+
+
 /*
  *
  * OpenType Layout Common Table Formats