diff --git a/ch04_keys.adoc b/ch04_keys.adoc
index 1fce182b..dbadb99e 100644
--- a/ch04_keys.adoc
+++ b/ch04_keys.adoc
@@ -977,7 +977,7 @@ combined execute about 2^80^ hash functions every hour.  They run a
 different hash function than HASH160, so their existing hardware can't
 create collision attacks for it, but the existence of the Bitcoin
 network proves that collision attacks against 160-bit functions like
-HASH160 are practical.  Bitcoin miners have spent the equivalent of
+HASH160 are ((("HASH160")))practical.  Bitcoin miners have spent the equivalent of
 billions of US dollars on special hardware, so creating a collision
 attack wouldn't be cheap, but there are organizations that expect to
 receive billions of dollars in bitcoins to addresses generated by