diff --git a/extensions/web/08_text_encoding.js b/extensions/web/08_text_encoding.js
index 4db1af29ac..7b2c974974 100644
--- a/extensions/web/08_text_encoding.js
+++ b/extensions/web/08_text_encoding.js
@@ -158,7 +158,7 @@
       const prefix = "Failed to execute 'encode' on 'TextEncoder'";
       input = webidl.converters.USVString(input, {
         prefix,
-        context: "Argument 2",
+        context: "Argument 1",
       });
       return core.encode(input);
     }