diff --git a/activesupport/test/core_ext/string_ext_test.rb b/activesupport/test/core_ext/string_ext_test.rb
index d3f52c04c4c80..8437ef1347bc6 100644
--- a/activesupport/test/core_ext/string_ext_test.rb
+++ b/activesupport/test/core_ext/string_ext_test.rb
@@ -465,7 +465,7 @@ def to_s
 
   test "Concatting with % doesn't modify a string" do
     @other_string = ["<p>", "<b>", "<h1>"]
-    "%s %s %s".html_safe % @other_string
+    _ = "%s %s %s".html_safe % @other_string
 
     assert_equal ["<p>", "<b>", "<h1>"], @other_string
   end