diff --git a/test_examples/test_helper.rb b/test_examples/test_helper.rb
index <HASH>..<HASH> 100644
--- a/test_examples/test_helper.rb
+++ b/test_examples/test_helper.rb
@@ -3,8 +3,12 @@ require 'minitest/autorun'
 require 'knapsack'
 
 if RUBY_VERSION == "1.9.3"
-  Minitest = MiniTest
-  Minitest::Test = MiniTest::Unit::TestCase
+  unless defined? Minitest
+    Minitest = MiniTest
+  end
+  unless defined? Minitest::Test
+    Minitest::Test = MiniTest::Unit::TestCase
+  end
 end
 
 Knapsack.tracker.config({
Fix warnings in Ruby <I> tests