diff --git a/lib/oj/mimic.rb b/lib/oj/mimic.rb
index c2882e39..e28c66d4 100644
--- a/lib/oj/mimic.rb
+++ b/lib/oj/mimic.rb
@@ -1,11 +1,7 @@
 # frozen_string_literal: false
 
 require 'bigdecimal'
-begin
-  require 'ostruct'
-rescue Exception
-  # ignore
-end
+require 'ostruct'
 
 module Oj
 
diff --git a/oj.gemspec b/oj.gemspec
index 232ee9cb..a44c9725 100644
--- a/oj.gemspec
+++ b/oj.gemspec
@@ -30,6 +30,7 @@ Gem::Specification.new do |s|
   s.rdoc_options = ['--title', 'Oj', '--main', 'README.md']
 
   s.add_runtime_dependency 'bigdecimal', '>= 3.0'
+  s.add_runtime_dependency 'ostruct', '>= 0.2'
   s.add_development_dependency 'minitest', '~> 5'
   s.add_development_dependency 'rake-compiler', '>= 0.9', '< 2.0'
   s.add_development_dependency 'test-unit', '~> 3.0'