diff --git a/doc/arm/Bv9ARM-book.xml b/doc/arm/Bv9ARM-book.xml
index 170cb6d430..5b3cc3ecda 100644
--- a/doc/arm/Bv9ARM-book.xml
+++ b/doc/arm/Bv9ARM-book.xml
@@ -6383,7 +6383,7 @@ options {
 		<para>
 		  If set, this is a shared secret used for generating
 		  and verifying Source Identity Token EDNS options
-		  within a anycast cluster.  If not set the system
+		  within an anycast cluster.  If not set, the system
 		  will generate a random secret at startup.  The
 		  shared secret is encoded as a hex string and needs
 		  to be 128 bits for AES128, 160 bits for SHA1 and