diff --git a/Gemfile b/Gemfile
index f4756de..cbbd68c 100644
--- a/Gemfile
+++ b/Gemfile
@@ -3,4 +3,4 @@ gem 'fastreader'
 gem 'nokogiri'
 gem 'rack', '~> 1.1'
 gem 'rspec'
-gem 'pdfkit', '~> 0.5'
+gem 'pdfkit', '~> 0.5', '>= 0.5.3'
diff --git a/Gemfile.lock b/Gemfile.lock
index 1702514..3760cec 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -36,7 +36,7 @@ GEM
     minitest (5.9.1)
     nokogiri (1.6.8.1)
       mini_portile2 (~> 2.1.0)
-    pdfkit (0.5.2)
+    pdfkit (0.8.7.3)
     rack (1.6.4)
     rake (11.3.0)
     rspec (3.5.0)
@@ -66,9 +66,9 @@ PLATFORMS
 DEPENDENCIES
   fastreader
   nokogiri
-  pdfkit (= 0.5.2)
+  pdfkit (~> 0.5, >= 0.5.3)
   rack (~> 1.1)
   rspec
 
 BUNDLED WITH
-   1.13.6
+   2.3.27