diff --git a/Gemfile.lock b/Gemfile.lock
index 0ca273a..f14ba5b 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -2,8 +2,8 @@ GEM
   remote: https://rubygems.org/
   specs:
     Ascii85 (1.0.3)
-    addressable (2.7.0)
-      public_suffix (>= 2.0.2, < 5.0)
+    addressable (2.8.1)
+      public_suffix (>= 2.0.2, < 6.0)
     afm (0.2.2)
     asciidoctor (2.0.12)
     asciidoctor-epub3 (1.5.0.alpha.19)
@@ -76,7 +76,7 @@ GEM
     prawn-templates (0.1.2)
       pdf-reader (~> 2.0)
       prawn (~> 2.2)
-    public_suffix (4.0.6)
+    public_suffix (5.0.0)
     pygments.rb (1.2.1)
       multi_json (>= 1.0.0)
     rainbow (3.0.0)
@@ -94,6 +94,7 @@ GEM
 
 PLATFORMS
   x86_64-darwin-19
+  x86_64-linux
 
 DEPENDENCIES
   asciidoctor (= 2.0.12)