diff --git a/.travis.yml b/.travis.yml
index f4ba903..971f8a7 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -19,6 +19,7 @@ install:
     - npm install gitbook-plugin-anchors
     - npm install gitbook-plugin-image-class
     - npm install gitbook-plugin-codesnippet
+    - npm install gitbook-plugin-last-modified
 
 script:
     - npm install honkit