diff --git a/protocols/lisp/ctl/pom.xml b/protocols/lisp/ctl/pom.xml
index 82df5d1..a838150 100644
--- a/protocols/lisp/ctl/pom.xml
+++ b/protocols/lisp/ctl/pom.xml
@@ -68,6 +68,11 @@
             <classifier>tests</classifier>
             <scope>test</scope>
         </dependency>
+        <dependency>
+            <groupId>com.googlecode.concurrent-trees</groupId>
+            <artifactId>concurrent-trees</artifactId>
+            <version>2.6.0</version>
+        </dependency>
 
     </dependencies>