diff --git a/Gemfile b/Gemfile
index e19132dcf..0b4c4abc0 100644
--- a/Gemfile
+++ b/Gemfile
@@ -32,7 +32,7 @@ gem 'rails-settings-cached',     '0.4.1' # for settings
 
 # html-xml
 gem 'haml-rails', '0.9.0' # haml for views
-gem 'nokogiri', '~> 1.7'
+gem 'nokogiri'
 
 # style
 gem 'bootstrap-sass', '3.3.5.1' # bootstrap style
diff --git a/Gemfile.lock b/Gemfile.lock
index 052061bc2..18a92eb54 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -266,7 +266,7 @@ GEM
     mina (0.3.1)
       open4 (~> 1.3.4)
       rake
-    mini_portile2 (2.1.0)
+    mini_portile2 (2.3.0)
     minitest (5.10.2)
     monetize (1.6.0)
       money (~> 6.8)
@@ -281,8 +281,8 @@ GEM
     multi_json (1.12.1)
     multi_xml (0.6.0)
     netrc (0.11.0)
-    nokogiri (1.7.2)
-      mini_portile2 (~> 2.1.0)
+    nokogiri (1.8.1)
+      mini_portile2 (~> 2.3.0)
     nori (2.6.0)
     nprogress-rails (0.1.6.7)
     open4 (1.3.4)
@@ -529,7 +529,7 @@ DEPENDENCIES
   liquid (= 3.0.6)
   mina (= 0.3.1)
   money-rails
-  nokogiri (~> 1.7)
+  nokogiri
   nprogress-rails (= 0.1.6.7)
   paper_trail!
   pdfkit (= 0.6.2)