diff --git a/encoding/idlharness.any.js b/encoding/idlharness.any.js
index 7a057f14e3a78c..acd100c43b461c 100644
--- a/encoding/idlharness.any.js
+++ b/encoding/idlharness.any.js
@@ -4,7 +4,7 @@
 
 idl_test(
   ['encoding'],
-  [], // No deps
+  ['streams'],
   idl_array => {
     idl_array.add_objects({
       TextEncoder: ['new TextEncoder()'],
diff --git a/interfaces/encoding.idl b/interfaces/encoding.idl
index bae48f11993e5f..7585cb3717c9aa 100644
--- a/interfaces/encoding.idl
+++ b/interfaces/encoding.idl
@@ -44,11 +44,6 @@ interface TextEncoder {
 };
 TextEncoder includes TextEncoderCommon;
 
-interface mixin GenericTransformStream {
-  readonly attribute ReadableStream readable;
-  readonly attribute WritableStream writable;
-};
-
 [Exposed=(Window,Worker)]
 interface TextDecoderStream {
   constructor(optional DOMString label = "utf-8", optional TextDecoderOptions options = {});