diff --git a/ch06.asciidoc b/ch06.asciidoc
index 832c93ff..50ee9377 100644
--- a/ch06.asciidoc
+++ b/ch06.asciidoc
@@ -227,7 +227,7 @@ To fully understand Alice's transaction we had to retrieve the previous transact
 
 ===== Transaction serialization—inputs
 
-When transactions are serialized for transmission on the network, their inputs are encoded into a byte-stream as shown in <<tx_in_structure>>.
+((("serialization", "inputs")))When transactions are serialized for transmission on the network, their inputs are encoded into a byte-stream as shown in <<tx_in_structure>>.
 
 [[tx_in_structure]]
 .Transaction input serialization