1 files changed, 26 insertions, 1 deletions
diff --git a/lib/_stream_writable.js b/lib/_stream_writable.js
index 1232742eb9..22aee3236c 100644
--- a/lib/_stream_writable.js
+++ b/lib/_stream_writable.js
@@ -647,7 +647,7 @@ function needFinish(state) {
 function callFinal(stream, state) {
   state.sync = true;
   state.pendingcb++;
-  stream._final((err) => {
+  const result = stream._final((err) => {
     state.pendingcb--;
     if (err) {
       for (const callback of state[kOnFinished].splice(0)) {
@@ -664,6 +664,31 @@ function callFinal(stream, state) {
       process.nextTick(finish, stream, state);
     }
   });
+  if (result !== undefined && result !== null) {
+    try {
+      const then = result.then;
+      if (typeof then === 'function') {
+        then.call(
+          result,
+          function() {
+            if (state.prefinished)
+              return;
+            state.prefinish = true;
+            process.nextTick(() => stream.emit('prefinish'));
+            state.pendingcb++;
+            process.nextTick(finish, stream, state);
+          },
+          function(err) {
+            for (const callback of state[kOnFinished].splice(0)) {
+              process.nextTick(callback, err);
+            }
+            process.nextTick(errorOrDestroy, stream, err, state.sync);
+          });
+      }
+    } catch (err) {
+      process.nextTick(errorOrDestroy, stream, err, state.sync);
+    }
+  }
   state.sync = false;
 }