diff --git a/src/Executor/Promise/Adapter/SyncPromiseAdapter.php b/src/Executor/Promise/Adapter/SyncPromiseAdapter.php
index 1b3dd31..35341b3 100644
--- a/src/Executor/Promise/Adapter/SyncPromiseAdapter.php
+++ b/src/Executor/Promise/Adapter/SyncPromiseAdapter.php
@@ -96,6 +96,7 @@ class SyncPromiseAdapter implements PromiseAdapter
 
         foreach ($promisesOrValues as $index => $promiseOrValue) {
             if ($promiseOrValue instanceof Promise) {
+                $result[$index] = null;
                 $promiseOrValue->then(
                     function($value) use ($index, &$count, $total, &$result, $all) {
                         $result[$index] = $value;
diff --git a/tests/Executor/Promise/SyncPromiseAdapterTest.php b/tests/Executor/Promise/SyncPromiseAdapterTest.php
index c94271e..a192409 100644
--- a/tests/Executor/Promise/SyncPromiseAdapterTest.php
+++ b/tests/Executor/Promise/SyncPromiseAdapterTest.php
@@ -186,18 +186,18 @@ class SyncPromiseAdapterTest extends \PHPUnit_Framework_TestCase
             }
         );
 
-        $this->assertEquals($onFulfilledCalled, false);
-        $this->assertEquals($onRejectedCalled, false);
+        $this->assertSame($onFulfilledCalled, false);
+        $this->assertSame($onRejectedCalled, false);
 
         SyncPromise::runQueue();
 
         if ($expectedNextState !== SyncPromise::PENDING) {
-            $this->assertEquals(!$expectedNextReason, $onFulfilledCalled);
-            $this->assertEquals(!!$expectedNextReason, $onRejectedCalled);
+            $this->assertSame(!$expectedNextReason, $onFulfilledCalled);
+            $this->assertSame(!!$expectedNextReason, $onRejectedCalled);
         }
 
-        $this->assertEquals($expectedNextValue, $actualNextValue);
-        $this->assertEquals($expectedNextReason, $actualNextReason);
-        $this->assertEquals($expectedNextState, $promise->adoptedPromise->state);
+        $this->assertSame($expectedNextValue, $actualNextValue);
+        $this->assertSame($expectedNextReason, $actualNextReason);
+        $this->assertSame($expectedNextState, $promise->adoptedPromise->state);
     }
 }