diff --git a/ch02_overview.adoc b/ch02_overview.adoc
index c49fe8ee..09175480 100644
--- a/ch02_overview.adoc
+++ b/ch02_overview.adoc
@@ -461,7 +461,7 @@ validated by full nodes. See
 <<mining>> for a detailed explanation.
 
 Bitcoin's system of counterfeit protection is based on computation.
-Transactions are bundled((("transactions", "blocks")))((("blocks"))) into _blocks_.  Blocks have a very small header
+Transactions are bundled((("transactions", "in blocks", secondary-sortas="blocks")))((("blocks"))) into _blocks_.  Blocks have a very small header
 that must be formed in a very specific way, requiring an enormous
 amount of computation to get right--but only a small amount of
 computation to verify as correct.