diff --git a/lib/hdb/hdb.h b/lib/hdb/hdb.h
index 2a3d1c4bb..87377513d 100644
--- a/lib/hdb/hdb.h
+++ b/lib/hdb/hdb.h
@@ -77,6 +77,7 @@ enum hdb_lockop{ HDB_RLOCK, HDB_WLOCK };
 #define HDB_F_DELAY_NEW_KEYS	0x08000	/* apply [hdb] new_service_key_delay */
 #define HDB_F_SYNTHETIC_OK	0x10000	/* synthetic principal for PKINIT or GSS preauth OK */
 #define HDB_F_GET_FAST_COOKIE	0x20000	/* fetch the FX-COOKIE key (not a normal principal) */
+#define HDB_F_ARMOR_PRINCIPAL	0x40000	/* fetch is for the client of an armor ticket */
 
 /* hdb_capability_flags */
 #define HDB_CAP_F_HANDLE_ENTERPRISE_PRINCIPAL 1