diff --git a/test/test_rake_file_utils.rb b/test/test_rake_file_utils.rb
index 42dccac6c..3af5e96f1 100644
--- a/test/test_rake_file_utils.rb
+++ b/test/test_rake_file_utils.rb
@@ -342,40 +342,33 @@ def test_sh_if_a_command_exits_with_error_status_sh_echoes_it_fully
     end
   end
 
-  # https://github.com/seattlerb/minitest/blob/21d9e804b63c619f602f3f4ece6c71b48974707a/lib/minitest/assertions.rb#L188
-  def _synchronize
-    yield
-  end
-
-  # https://github.com/seattlerb/minitest/blob/21d9e804b63c619f602f3f4ece6c71b48974707a/lib/minitest/assertions.rb#L546
+  # Originally copied from minitest/assertions.rb
   def capture_subprocess_io
-    _synchronize do
-      begin
-        require "tempfile"
+    begin
+      require "tempfile"
 
-        captured_stdout = Tempfile.new("out")
-        captured_stderr = Tempfile.new("err")
+      captured_stdout = Tempfile.new("out")
+      captured_stderr = Tempfile.new("err")
 
-        orig_stdout = $stdout.dup
-        orig_stderr = $stderr.dup
-        $stdout.reopen captured_stdout
-        $stderr.reopen captured_stderr
+      orig_stdout = $stdout.dup
+      orig_stderr = $stderr.dup
+      $stdout.reopen captured_stdout
+      $stderr.reopen captured_stderr
 
-        yield
+      yield
 
-        $stdout.rewind
-        $stderr.rewind
+      $stdout.rewind
+      $stderr.rewind
 
-        return captured_stdout.read, captured_stderr.read
-      ensure
-        $stdout.reopen orig_stdout
-        $stderr.reopen orig_stderr
+      [captured_stdout.read, captured_stderr.read]
+    ensure
+      $stdout.reopen orig_stdout
+      $stderr.reopen orig_stderr
 
-        orig_stdout.close
-        orig_stderr.close
-        captured_stdout.close!
-        captured_stderr.close!
-      end
+      orig_stdout.close
+      orig_stderr.close
+      captured_stdout.close!
+      captured_stderr.close!
     end
   end