diff --git a/Gemfile b/Gemfile
index 1cc952b..67c0c41 100644
--- a/Gemfile
+++ b/Gemfile
@@ -2,3 +2,8 @@ source "https://rubygems.org"
 
 # Specify your gem's dependencies in itamae-plugin-resource-encrypted_remote_file.gemspec
 gemspec
+
+if Gem::Version.create(RUBY_VERSION) < Gem::Version.create("2.4.0")
+  # base64 0.1.1+ doesn't work on Ruby 2.4+
+  gem "base64", "< 0.1.1"
+end