diff --git a/test/test_error_highlight.rb b/test/test_error_highlight.rb
index 6136bcd..b75bf6d 100644
--- a/test/test_error_highlight.rb
+++ b/test/test_error_highlight.rb
@@ -1361,7 +1361,7 @@ def test_errors_on_terminal_window_smaller_than_min_width
     min_snippet_width = ErrorHighlight::DefaultFormatter::MIN_SNIPPET_WIDTH
 
     warning = nil
-    original_warn = Warning.method(:warn)
+    original_warn = Warning.instance_method(:warn)
     Warning.class_eval do
       remove_method(:warn)
       define_method(:warn) {|str| warning = str}