diff --git a/include/openssl/x509v3.h b/include/openssl/x509v3.h
index f21ce7c..1d8ef87 100644
--- a/include/openssl/x509v3.h
+++ b/include/openssl/x509v3.h
@@ -355,6 +355,7 @@
 # define EXFLAG_SI               0x20
 # define EXFLAG_V1               0x40
 # define EXFLAG_INVALID          0x80
+/* EXFLAG_SET is set to indicate that some values have been precomputed */
 # define EXFLAG_SET              0x100
 # define EXFLAG_CRITICAL         0x200
 # define EXFLAG_PROXY            0x400