diff --git a/Retention/Gemfile b/Retention/Gemfile
index 099d44a..274af22 100644
--- a/Retention/Gemfile
+++ b/Retention/Gemfile
@@ -1,5 +1,5 @@
 source 'https://rubygems.org'
 gem 'keen'
 gem 'activesupport', require: "active_support/all" #for datetime calculation e.g. weeks.ago.at_beginning_of_week
-gem 'rubyzip', '~>  0.9.9'
+gem 'rubyzip', '~> 1.3.0'
 gem 'simple_xlsx_writer', require: "simple_xlsx"   #for outputting excel files
diff --git a/Retention/Gemfile.lock b/Retention/Gemfile.lock
index b974e54..4947a4d 100644
--- a/Retention/Gemfile.lock
+++ b/Retention/Gemfile.lock
@@ -16,7 +16,7 @@ GEM
       multi_json (~> 1.3)
     minitest (5.4.0)
     multi_json (1.10.1)
-    rubyzip (0.9.9)
+    rubyzip (1.3.0)
     simple_xlsx_writer (0.5.3)
       fast_xs (>= 0.7.3)
       rubyzip (>= 0.9.4)
@@ -30,5 +30,5 @@ PLATFORMS
 DEPENDENCIES
   activesupport
   keen
-  rubyzip (~> 0.9.9)
+  rubyzip (~> 1.3.0)
   simple_xlsx_writer