diff --git a/Gemfile.lock b/Gemfile.lock
index deb1e5b..725c335 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -25,16 +25,16 @@ GEM
     concurrent-ruby (1.1.7)
     css_parser (1.7.1)
       addressable
-    gepub (1.0.13)
-      nokogiri (>= 1.8.2, < 1.12)
+    gepub (1.0.15)
+      nokogiri (>= 1.8.2, < 2.0)
       rubyzip (> 1.1.1, < 2.4)
     hashery (2.1.2)
     mime-types (3.3.1)
       mime-types-data (~> 3.2015)
     mime-types-data (3.2020.0512)
-    mini_portile2 (2.5.1)
-    nokogiri (1.11.4)
-      mini_portile2 (~> 2.5.0)
+    mini_portile2 (2.8.0)
+    nokogiri (1.13.6)
+      mini_portile2 (~> 2.8.0)
       racc (~> 1.4)
     pdf-core (0.7.0)
     pdf-reader (2.4.0)
@@ -58,10 +58,10 @@ GEM
       pdf-reader (~> 2.0)
       prawn (~> 2.2)
     public_suffix (4.0.5)
-    racc (1.5.2)
+    racc (1.6.0)
     rouge (3.22.0)
     ruby-rc4 (0.1.5)
-    rubyzip (2.3.0)
+    rubyzip (2.3.2)
     safe_yaml (1.0.5)
     thread_safe (0.3.6)
     treetop (1.6.10)