diff --git a/Gemfile.lock b/Gemfile.lock
index 2752f5f9f2..50071379b8 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -154,7 +154,7 @@ GEM
       coffee-script-source
       execjs
     coffee-script-source (1.12.2)
-    combine_pdf (1.0.16)
+    combine_pdf (1.0.21)
       ruby-rc4 (>= 0.1.5)
     compass (1.0.3)
       chunky_png (~> 1.2)