1 files changed, 3 insertions, 0 deletions
diff --git a/test/ruby/test_io.rb b/test/ruby/test_io.rb
index 4dc7599b99..8eb94e367a 100644
--- a/test/ruby/test_io.rb
+++ b/test/ruby/test_io.rb
@@ -2981,6 +2981,9 @@ End
     File.unlink(path)
     IO.write(path, "foo", encoding: Encoding::UTF_32BE)
     assert_equal("\0\0\0f\0\0\0o\0\0\0o", File.binread(path))
+    assert_raise(TypeError) {
+      IO.write(path, "foo", Object.new => Object.new)
+    }
   ensure
     t.close!
   end