diff --git a/src/main/FIO.ts b/src/main/FIO.ts
index 2d702e4a..1cd70502 100644
--- a/src/main/FIO.ts
+++ b/src/main/FIO.ts
@@ -2,6 +2,7 @@
  * Created by tushar on 2019-05-20
  */
 
+import {debug} from 'debug'
 import {Either, List, Option} from 'standard-data-structures'
 import {ICancellable} from 'ts-scheduler'
 
@@ -13,6 +14,8 @@ import {IRuntime} from '../runtimes/IRuntime'
 import {Await} from './Await'
 import {Instruction, Tag} from './Instructions'
 
+const D = debug('fio:core')
+
 export type NoEnv = unknown
 
 /**
@@ -56,7 +59,7 @@ export type NodeJSCallback<A> = (
  */
 export class FIO<E1 = unknown, A1 = unknown, R1 = NoEnv> {
   /**
-   * Safely converts an interuptable IO to non-interruptable one.
+   * Safely converts an interuptable IO to non-interuptable one.
    */
   public get asEither(): FIO<never, Either<E1, A1>, R1> {
     return this.map(Either.right).catch(_ => FIO.of(Either.left(_)))
@@ -660,15 +663,24 @@ export class FIO<E1 = unknown, A1 = unknown, R1 = NoEnv> {
     cb2: (exit: Either<E2, A2>, fiber: Fiber<E1, A1>) => IO<E4, A4>
   ): FIO<E3 | E4, A3 | A4, R1 & R2> {
     return Await.of<E3 | E4, A3 | A4>().chain(done =>
-      this.fork.zip(that.fork).chain(({0: f1, 1: f2}) => {
-        const resume1 = f1.await.chain(exit =>
-          Option.isSome(exit) ? done.set(cb1(exit.value, f2)) : FIO.of(true)
-        )
-        const resume2 = f2.await.chain(exit =>
-          Option.isSome(exit) ? done.set(cb2(exit.value, f1)) : FIO.of(true)
-        )
+      this.fork.zip(that.fork).chain(([L, R]) => {
+        D('zip', 'fiber L', L.id, '& fiber R', R.id)
+        const resume1 = L.await.chain(exit => {
+          D('zip', 'L cb')
+
+          return Option.isSome(exit)
+            ? done.set(cb1(exit.value, R))
+            : FIO.of(true)
+        })
+        const resume2 = R.await.chain(exit => {
+          D('zip', 'R cb')
+
+          return Option.isSome(exit)
+            ? done.set(cb2(exit.value, L))
+            : FIO.of(true)
+        })
 
-        return resume1.and(resume2).and(done.get)
+        return resume1.fork.and(resume2.fork).and(done.get)
       })
     )
   }
diff --git a/test/FIO.test.ts b/test/FIO.test.ts
index 485d0159..b43884b0 100644
--- a/test/FIO.test.ts
+++ b/test/FIO.test.ts
@@ -622,7 +622,7 @@ describe('FIO', () => {
       assert.deepEqual(snapshot.timeline, ['A@1001', 'B@2001'])
     })
 
-    it('should complete when both complete', () => {
+    it('should complete when either complete', () => {
       const snapshot = new Snapshot()
 
       const F1 = snapshot.mark('A').delay(1000)
@@ -633,7 +633,7 @@ describe('FIO', () => {
         F1.raceWith(F2, FIO.void, FIO.void).and(snapshot.mark('C'))
       )
 
-      assert.deepEqual(snapshot.timeline, ['A@1001', 'B@2001', 'C@2001'])
+      assert.sameDeepMembers(snapshot.timeline, ['A@1001', 'B@2001', 'C@1001'])
     })
 
     context('when slower is cancelled', () => {