diff --git a/ch06.asciidoc b/ch06.asciidoc
index e0e85b47..f60dc9cc 100644
--- a/ch06.asciidoc
+++ b/ch06.asciidoc
@@ -692,7 +692,7 @@ This is not just a theoretical possibility. We have seen this issue lead to expo
 
 ((("warnings and cautions", "random number generation")))((("deterministic initialization")))To avoid this vulnerability, the industry best practice is to not generate _k_ with a random-number generator seeded with entropy, but instead to use a deterministic-random process seeded with the transaction data itself. This ensures that each transaction produces a different _k_. ((("RFC 6979")))The industry-standard algorithm for deterministic initialization of _k_ is defined in https://tools.ietf.org/html/rfc6979[RFC 6979], published by the Internet Engineering Task Force.
 
-If you are implementing an algorithm to sign transactions in bitcoin, you _must_ use RFC6979 or a similarly deterministic-random algorithm to ensure you generate a different _k_ for each transaction.((("", startref="Tdigsig06")))
+If you are implementing an algorithm to sign transactions in bitcoin, you _must_ use RFC 6979 or a similarly deterministic-random algorithm to ensure you generate a different _k_ for each transaction.((("", startref="Tdigsig06")))
 
 === Bitcoin Addresses, Balances, and Other Abstractions