diff --git a/docs-book/Gemfile.lock b/docs-book/Gemfile.lock
index e90ac4c..1fe3ef6 100644
--- a/docs-book/Gemfile.lock
+++ b/docs-book/Gemfile.lock
@@ -6,8 +6,8 @@ GEM
       minitest (~> 5.1)
       thread_safe (~> 0.3, >= 0.3.4)
       tzinfo (~> 1.1)
-    addressable (2.5.2)
-      public_suffix (>= 2.0.2, < 4.0)
+    addressable (2.8.1)
+      public_suffix (>= 2.0.2, < 6.0)
     ansi (1.5.0)
     backports (3.11.1)
     bookbindery (10.1.12)
@@ -165,7 +165,7 @@ GEM
     padrino-support (0.13.3.4)
       activesupport (>= 3.1)
     parallel (1.12.1)
-    public_suffix (3.0.1)
+    public_suffix (5.0.0)
     puma (3.11.2)
     rack (1.6.8)
     rack-livereload (0.3.16)