diff --git a/index.bs b/index.bs
index ced85a05c..bff861430 100644
--- a/index.bs
+++ b/index.bs
@@ -2649,7 +2649,7 @@ WritableStream(<var>underlyingSink</var> = {}, { <var>size</var>, <var>highWater
       and put it in an errored state. It should clean up any held resources, much like <code>close</code>, but perhaps
       with some custom handling. Unlike <code>close</code>, <code>abort</code> will be called even if writes are queued
       up; those <a>chunks</a> will be thrown away. If this process is asynchronous, it can return a promise to signal
-      success or failure. If no abort method is passed, by default the <code>close</code> method will be called instead.
+      success or failure.
   </ul>
 
   The <code>controller</code> object passed to <code>start</code>, <code>write</code> and <code>close</code> is an
@@ -3321,8 +3321,8 @@ nothrow>WritableStreamDefaultControllerAbort ( <var>controller</var>, <var>reaso
 
 <emu-alg>
   1. Set _controller_.[[queue]] to a new empty List.
-  1. Let _sinkAbortPromise_ be ! PromiseInvokeOrFallbackOrNoop(_controller_.[[underlyingSink]],
-     `"abort"`, « _reason_ », `"close"`, « _controller_ »).
+  1. Let _sinkAbortPromise_ be ! PromiseInvokeOrNoop(_controller_.[[underlyingSink]], `"abort"`, «
+    _reason_ »).
   1. Return the result of transforming _sinkAbortPromise_ by a fulfillment handler that returns
     *undefined*.
 </emu-alg>
@@ -3722,30 +3722,6 @@ A few abstract operations are used in this specification for utility purposes. W
   1. Return *true*.
 </emu-alg>
 
-<h4 id="promise-invoke-or-fallback-or-noop" aoid="PromiseInvokeOrFallbackOrNoop" nothrow>PromiseInvokeOrFallbackOrNoop (
-<var>O</var>, <var>P1</var>, <var>args1</var>, <var>P2</var>, <var>args2</var> )</h4>
-
-<div class="note">
-  PromiseInvokeOrFallbackOrNoop is a specialized version of <a>promise-calling</a> that works on methods, calls a
-  fallback method if the first method is not present, and returns a promise for <emu-val>undefined</emu-val> when
-  neither method is present.
-</div>
-
-<emu-alg>
-  1. Assert: _O_ is not *undefined*.
-  1. Assert: ! IsPropertyKey(_P1_) is *true*.
-  1. Assert: _args1_ is a List.
-  1. Assert: ! IsPropertyKey(_P2_) is *true*.
-  1. Assert: _args2_ is a List.
-  1. Let _method_ be GetV(_O_, _P1_).
-  1. If _method_ is an abrupt completion, return <a>a promise rejected with</a> _method_.[[Value]].
-  1. Let _method_ be _method_.[[Value]].
-  1. If _method_ is *undefined*, return ! PromiseInvokeOrNoop(_O_, _P2_, _args2_).
-  1. Let _returnValue_ be Call(_method_, _O_, _args1_).
-  1. If _returnValue_ is an abrupt completion, return <a>a promise rejected with</a> _returnValue_.[[Value]].
-  1. Otherwise, return <a>a promise resolved with</a> _returnValue_.[[Value]].
-</emu-alg>
-
 <h4 id="promise-invoke-or-noop" aoid="PromiseInvokeOrNoop" nothrow>PromiseInvokeOrNoop ( <var>O</var>, <var>P</var>,
 <var>args</var> )</h4>
 
@@ -4085,7 +4061,14 @@ promises returned by its <a lt="writable stream writer">writer</a>'s {{WritableS
       close() {
         return new Promise((resolve, reject) => {
           ws.onclose = resolve;
-          ws.close();
+          ws.close(1000);
+        });
+      },
+
+      abort(reason) {
+        return new Promise((resolve, reject) => {
+          ws.onclose = resolve;
+          ws.close(4000, reason && reason.message);
         });
       }
     });
@@ -4129,6 +4112,10 @@ an individual write succeeded or failed.
 
       close() {
         return fs.close(fd);
+      },
+
+      abort() {
+        return fs.close(fd);
       }
     });
   }
@@ -4223,7 +4210,14 @@ source abstractions.
         this._ws.close();
       });
     }
-  });
+
+    abort(reason) {
+      return new Promise((resolve, reject) => {
+        ws.onclose = resolve;
+        ws.close(4000, reason && reason.message);
+      });
+    }
+  }
 </code></pre>
 
 We can then use the objects created by this function to communicate with a remote web socket, using the standard stream
diff --git a/reference-implementation/lib/helpers.js b/reference-implementation/lib/helpers.js
index 28a47458e..5f48df1c4 100644
--- a/reference-implementation/lib/helpers.js
+++ b/reference-implementation/lib/helpers.js
@@ -100,16 +100,6 @@ exports.PromiseInvokeOrPerformFallback = (O, P, args, F, argsF) => {
   }
 };
 
-exports.PromiseInvokeOrFallbackOrNoop = (O, P1, args1, P2, args2) => {
-  assert(O !== undefined);
-  assert(IsPropertyKey(P1));
-  assert(Array.isArray(args1));
-  assert(IsPropertyKey(P2));
-  assert(Array.isArray(args2));
-
-  return exports.PromiseInvokeOrPerformFallback(O, P1, args1, exports.PromiseInvokeOrNoop, [O, P2, args2]);
-};
-
 // Not implemented correctly
 exports.SameRealmTransfer = O => O;
 
diff --git a/reference-implementation/lib/writable-stream.js b/reference-implementation/lib/writable-stream.js
index 79b931e11..aed008338 100644
--- a/reference-implementation/lib/writable-stream.js
+++ b/reference-implementation/lib/writable-stream.js
@@ -1,7 +1,7 @@
 'use strict';
 const assert = require('assert');
-const { InvokeOrNoop, PromiseInvokeOrNoop, PromiseInvokeOrFallbackOrNoop, ValidateAndNormalizeQueuingStrategy,
-        typeIsObject } = require('./helpers.js');
+const { InvokeOrNoop, PromiseInvokeOrNoop, ValidateAndNormalizeQueuingStrategy, typeIsObject } =
+  require('./helpers.js');
 const { rethrowAssertionErrorRejection } = require('./utils.js');
 const { DequeueValue, EnqueueValueWithSize, GetTotalQueueSize, PeekQueueValue } = require('./queue-with-sizes.js');
 
@@ -574,8 +574,7 @@ class WritableStreamDefaultController {
 function WritableStreamDefaultControllerAbort(controller, reason) {
   controller._queue = [];
 
-  const sinkAbortPromise = PromiseInvokeOrFallbackOrNoop(controller._underlyingSink, 'abort', [reason],
-                                                         'close', [controller]);
+  const sinkAbortPromise = PromiseInvokeOrNoop(controller._underlyingSink, 'abort', [reason]);
   return sinkAbortPromise.then(() => undefined);
 }
 
diff --git a/reference-implementation/to-upstream-wpts/writable-streams/aborting.js b/reference-implementation/to-upstream-wpts/writable-streams/aborting.js
index 87b25e72c..ee4eaeaef 100644
--- a/reference-implementation/to-upstream-wpts/writable-streams/aborting.js
+++ b/reference-implementation/to-upstream-wpts/writable-streams/aborting.js
@@ -250,15 +250,14 @@ promise_test(() => {
 }, 'Aborting a WritableStream after it is closed is a no-op');
 
 promise_test(t => {
+  // Testing that per https://github.com/whatwg/streams/issues/620#issuecomment-263483953 the fallback to close was
+  // removed.
+
   // Cannot use recordingWritableStream since it always has an abort
-  let controller;
-  let closeArgs;
+  let closeCalled = false;
   const ws = new WritableStream({
-    start(c) {
-      controller = c;
-    },
-    close(...args) {
-      closeArgs = args;
+    close() {
+      closeCalled = true;
     }
   });
 
@@ -267,9 +266,9 @@ promise_test(t => {
   writer.abort();
 
   return promise_rejects(t, new TypeError(), writer.closed, 'closed should reject with a TypeError').then(() => {
-    assert_array_equals(closeArgs, [controller], 'close must have been called, with the controller as its argument');
+    assert_false(closeCalled, 'close must not have been called');
   });
-}, 'WritableStream should call underlying sink\'s close if no abort is supplied');
+}, 'WritableStream should NOT call underlying sink\'s close if no abort is supplied (historical)');
 
 promise_test(() => {
   let thenCalled = false;
diff --git a/reference-implementation/to-upstream-wpts/writable-streams/general.js b/reference-implementation/to-upstream-wpts/writable-streams/general.js
index 891b2520a..c284338a3 100644
--- a/reference-implementation/to-upstream-wpts/writable-streams/general.js
+++ b/reference-implementation/to-upstream-wpts/writable-streams/general.js
@@ -173,7 +173,9 @@ promise_test(t => {
   const writer2 = ws2.getWriter();
   writer2.abort();
 
-  // Test PromiseInvokeOrFallbackOrNoop.
+  // Test abort() with a close underlying sink method present. (Historical; see
+  // https://github.com/whatwg/streams/issues/620#issuecomment-263483953 for what used to be
+  // tested here. But more coverage can't hurt.)
   const ws3 = new WritableStream({
     start: functionWithOverloads,
     write: functionWithOverloads,