diff --git a/ch01_intro.adoc b/ch01_intro.adoc
index e1bb237b..fd2833e7 100644
--- a/ch01_intro.adoc
+++ b/ch01_intro.adoc
@@ -179,7 +179,7 @@ their privacy. Most, however, take control of the Bitcoin keys from
 users in exchange for ease-of-use. It is inadvisable
 to store large amounts of bitcoin on third-party systems.
 
-Hardware signing devices:: Hardware signing devices are devices that can
+Hardware signing devices:: Hardware signing devices((("hardware signing devices"))) are devices that can
 store keys and sign transactions using special-purpose hardware and
 firmware. They usually
 connect to a desktop, mobile, or web wallet via USB cable,