diff --git a/ch11_blockchain.adoc b/ch11_blockchain.adoc
index bb4a81e2..f8ede214 100644
--- a/ch11_blockchain.adoc
+++ b/ch11_blockchain.adoc
@@ -361,7 +361,7 @@ Each block((("blockchain", "merkle trees", id="blockchain-merkle")))((("merkle t
 a summary of all the transactions in the block using a _merkle tree_.
 
 A _merkle tree_, also known
-as a _binary hash tree_, is a data structure used for efficiently
+as a _binary hash tree_, is ((("binary hash trees")))a data structure used for efficiently
 summarizing and verifying the integrity of large sets of data. Merkle
 trees are binary trees containing cryptographic hashes. The term "tree"
 is used in computer science to describe a branching data structure, but