diff --git a/Gemfile b/Gemfile
index 1aa98e4..3be9c3c 100644
--- a/Gemfile
+++ b/Gemfile
@@ -1,2 +1,2 @@
-source "http://rubygems.org"
+source "https://rubygems.org"
 gemspec
diff --git a/Gemfile.v0.12 b/Gemfile.v0.12
index 2978157..b910d4c 100644
--- a/Gemfile.v0.12
+++ b/Gemfile.v0.12
@@ -1,4 +1,4 @@
-source "http://rubygems.org"
+source "https://rubygems.org"
 
 gem 'json', '= 1.8.6'
 gem 'fluentd', '~> 0.12.0'