1 files changed, 1 insertions, 0 deletions

diff --git a/pom.xml b/pom.xml
index ec011df6..0315f997 100644
--- a/pom.xml
+++ b/pom.xml
@@ -39,6 +39,7 @@
         <module>chapter18</module>
         <module>chapter19</module>
         <module>chapter20</module>
+        <module>chapter21</module>
     </modules>
 
     <properties>