diff --git a/tool/lib/core_assertions.rb b/tool/lib/core_assertions.rb
index 2e4235fb69..a670c77310 100644
--- a/tool/lib/core_assertions.rb
+++ b/tool/lib/core_assertions.rb
@@ -24,13 +24,11 @@ module Test
     end
 
     module CoreAssertions
+      require_relative 'envutil'
+
       if defined?(MiniTest)
-        require_relative 'envutil'
         # for ruby core testing
         include MiniTest::Assertions
-
-        # Compatibility hack for assert_raise
-        Test::Unit::AssertionFailedError = MiniTest::Assertion
       else
         module MiniTest
           class Assertion < Exception; end
@@ -38,7 +36,6 @@ module Test
         end
 
         require 'pp'
-        require_relative 'envutil'
         include Test::Unit::Assertions
       end
 
diff --git a/tool/lib/test/unit/assertions.rb b/tool/lib/test/unit/assertions.rb
index c61f296da9..b99fb19adf 100644
--- a/tool/lib/test/unit/assertions.rb
+++ b/tool/lib/test/unit/assertions.rb
@@ -303,5 +303,9 @@ EOT
         template.gsub(/\G((?:[^\\]|\\.)*?)(\\)?\?/) { $1 + ($2 ? "?" : mu_pp(arguments.shift)) }
       end
     end
+
+    # Compatibility hack for assert_raise
+    AssertionFailedError = MiniTest::Assertion
+
   end
 end