diff --git a/Gemfile.lock b/Gemfile.lock
index e179d95..5b744c3 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -2,7 +2,6 @@ PATH
   remote: .
   specs:
     json_schemer (2.2.1)
-      base64
       bigdecimal
       hana (~> 1.3)
       regexp_parser (~> 2.0)
@@ -43,6 +42,7 @@ PLATFORMS
   ruby
 
 DEPENDENCIES
+  base64
   bundler (~> 2.0)
   csv
   i18n
diff --git a/json_schemer.gemspec b/json_schemer.gemspec
index 9b789dc..6b84785 100644
--- a/json_schemer.gemspec
+++ b/json_schemer.gemspec
@@ -22,6 +22,7 @@ Gem::Specification.new do |spec|
 
   spec.required_ruby_version = '>= 2.5'
 
+  spec.add_development_dependency "base64"
   spec.add_development_dependency "bundler", "~> 2.0"
   spec.add_development_dependency "rake", "~> 13.0"
   spec.add_development_dependency "minitest", "~> 5.0"
@@ -30,7 +31,6 @@ Gem::Specification.new do |spec|
   spec.add_development_dependency "i18n"
   spec.add_development_dependency "i18n-debug"
 
-  spec.add_runtime_dependency "base64"
   spec.add_runtime_dependency "bigdecimal"
   spec.add_runtime_dependency "hana", "~> 1.3"
   spec.add_runtime_dependency "regexp_parser", "~> 2.0"
diff --git a/lib/json_schemer.rb b/lib/json_schemer.rb
index 0123cf5..56a92ba 100644
--- a/lib/json_schemer.rb
+++ b/lib/json_schemer.rb
@@ -1,5 +1,4 @@
 # frozen_string_literal: true
-require 'base64'
 require 'bigdecimal'
 require 'ipaddr'
 require 'json'
diff --git a/lib/json_schemer/content.rb b/lib/json_schemer/content.rb
index 40ac328..05f2ca9 100644
--- a/lib/json_schemer/content.rb
+++ b/lib/json_schemer/content.rb
@@ -2,7 +2,7 @@
 module JSONSchemer
   module ContentEncoding
     BASE64 = proc do |instance|
-      [true, Base64.strict_decode64(instance)]
+      [true, instance.unpack1("m0")]
     rescue
       [false, nil]
     end
diff --git a/test/json_schemer_test.rb b/test/json_schemer_test.rb
index df6f7df..0c8dc82 100644
--- a/test/json_schemer_test.rb
+++ b/test/json_schemer_test.rb
@@ -1,4 +1,5 @@
 require 'test_helper'
+require 'base64'
 require 'csv'
 
 class JSONSchemerTest < Minitest::Test