diff --git a/src/Operation/Aggregate.php b/src/Operation/Aggregate.php
index 1916f8141..43f964410 100644
--- a/src/Operation/Aggregate.php
+++ b/src/Operation/Aggregate.php
@@ -229,10 +229,12 @@ public function __construct(string $databaseName, ?string $collectionName, array
             unset($options['batchSize']);
         }
 
-        /* Ignore batchSize for writes, since no documents are returned and a
-         * batchSize of zero could prevent the pipeline from executing. */
         if ($this->isWrite) {
+            /* Ignore batchSize for writes, since no documents are returned and
+             * a batchSize of zero could prevent the pipeline from executing. */
             unset($options['batchSize']);
+        } else {
+            unset($options['writeConcern']);
         }
 
         $this->databaseName = $databaseName;
@@ -366,16 +368,12 @@ private function executeCommand(Server $server, Command $command): Cursor
     {
         $options = [];
 
-        foreach (['readConcern', 'readPreference', 'session'] as $option) {
+        foreach (['readConcern', 'readPreference', 'session', 'writeConcern'] as $option) {
             if (isset($this->options[$option])) {
                 $options[$option] = $this->options[$option];
             }
         }
 
-        if ($this->isWrite && isset($this->options['writeConcern'])) {
-            $options['writeConcern'] = $this->options['writeConcern'];
-        }
-
         if (! $this->isWrite) {
             return $server->executeReadCommand($this->databaseName, $command, $options);
         }
diff --git a/tests/Collection/CollectionFunctionalTest.php b/tests/Collection/CollectionFunctionalTest.php
index 4a8b5bf6b..eeb4af16c 100644
--- a/tests/Collection/CollectionFunctionalTest.php
+++ b/tests/Collection/CollectionFunctionalTest.php
@@ -21,7 +21,7 @@
 use function call_user_func;
 use function is_scalar;
 use function json_encode;
-use function strchr;
+use function str_contains;
 use function usort;
 use function version_compare;
 
@@ -434,16 +434,30 @@ public function testMapReduce(): void
     public function collectionMethodClosures()
     {
         return [
-            [
+            'read-only aggregate' => [
                 function ($collection, $session, $options = []): void {
                     $collection->aggregate(
                         [['$match' => ['_id' => ['$lt' => 3]]]],
                         ['session' => $session] + $options
                     );
+                }, 'r',
+            ],
+
+            /* Disabled, as write aggregations are not supported in transactions
+            'read-write aggregate' => [
+                function ($collection, $session, $options = []): void {
+                    $collection->aggregate(
+                        [
+                            ['$match' => ['_id' => ['$lt' => 3]]],
+                            ['$merge' => $collection . '_out'],
+                        ],
+                        ['session' => $session] + $options
+                    );
                 }, 'rw',
             ],
+            */
 
-            [
+            'bulkWrite insertOne' => [
                 function ($collection, $session, $options = []): void {
                     $collection->bulkWrite(
                         [['insertOne' => [['test' => 'foo']]]],
@@ -453,7 +467,7 @@ function ($collection, $session, $options = []): void {
             ],
 
             /* Disabled, as count command can't be used in transactions
-            [
+            'count' => [
                 function($collection, $session, $options = []) {
                     $collection->count(
                         [],
@@ -463,7 +477,7 @@ function($collection, $session, $options = []) {
             ],
             */
 
-            [
+            'countDocuments' => [
                 function ($collection, $session, $options = []): void {
                     $collection->countDocuments(
                         [],
@@ -473,7 +487,7 @@ function ($collection, $session, $options = []): void {
             ],
 
             /* Disabled, as it's illegal to use createIndex command in transactions
-            [
+            'createIndex' => [
                 function($collection, $session, $options = []) {
                     $collection->createIndex(
                         ['test' => 1],
@@ -483,7 +497,7 @@ function($collection, $session, $options = []) {
             ],
             */
 
-            [
+            'deleteMany' => [
                 function ($collection, $session, $options = []): void {
                     $collection->deleteMany(
                         ['test' => 'foo'],
@@ -492,7 +506,7 @@ function ($collection, $session, $options = []): void {
                 }, 'w',
             ],
 
-            [
+            'deleteOne' => [
                 function ($collection, $session, $options = []): void {
                     $collection->deleteOne(
                         ['test' => 'foo'],
@@ -501,7 +515,7 @@ function ($collection, $session, $options = []): void {
                 }, 'w',
             ],
 
-            [
+            'distinct' => [
                 function ($collection, $session, $options = []): void {
                     $collection->distinct(
                         '_id',
@@ -512,7 +526,7 @@ function ($collection, $session, $options = []): void {
             ],
 
             /* Disabled, as it's illegal to use drop command in transactions
-            [
+            'drop' => [
                 function($collection, $session, $options = []) {
                     $collection->drop(
                         ['session' => $session] + $options
@@ -522,7 +536,7 @@ function($collection, $session, $options = []) {
             */
 
             /* Disabled, as it's illegal to use dropIndexes command in transactions
-            [
+            'dropIndex' => [
                 function($collection, $session, $options = []) {
                     $collection->dropIndex(
                         '_id_1',
@@ -532,7 +546,7 @@ function($collection, $session, $options = []) {
             ], */
 
             /* Disabled, as it's illegal to use dropIndexes command in transactions
-            [
+            'dropIndexes' => [
                 function($collection, $session, $options = []) {
                     $collection->dropIndexes(
                         ['session' => $session] + $options
@@ -542,7 +556,7 @@ function($collection, $session, $options = []) {
             */
 
             /* Disabled, as count command can't be used in transactions
-            [
+            'estimatedDocumentCount' => [
                 function($collection, $session, $options = []) {
                     $collection->estimatedDocumentCount(
                         ['session' => $session] + $options
@@ -551,7 +565,7 @@ function($collection, $session, $options = []) {
             ],
             */
 
-            [
+            'find' => [
                 function ($collection, $session, $options = []): void {
                     $collection->find(
                         ['test' => 'foo'],
@@ -560,7 +574,7 @@ function ($collection, $session, $options = []): void {
                 }, 'r',
             ],
 
-            [
+            'findOne' => [
                 function ($collection, $session, $options = []): void {
                     $collection->findOne(
                         ['test' => 'foo'],
@@ -569,7 +583,7 @@ function ($collection, $session, $options = []): void {
                 }, 'r',
             ],
 
-            [
+            'findOneAndDelete' => [
                 function ($collection, $session, $options = []): void {
                     $collection->findOneAndDelete(
                         ['test' => 'foo'],
@@ -578,7 +592,7 @@ function ($collection, $session, $options = []): void {
                 }, 'w',
             ],
 
-            [
+            'findOneAndReplace' => [
                 function ($collection, $session, $options = []): void {
                     $collection->findOneAndReplace(
                         ['test' => 'foo'],
@@ -588,7 +602,7 @@ function ($collection, $session, $options = []): void {
                 }, 'w',
             ],
 
-            [
+            'findOneAndUpdate' => [
                 function ($collection, $session, $options = []): void {
                     $collection->findOneAndUpdate(
                         ['test' => 'foo'],
@@ -598,7 +612,7 @@ function ($collection, $session, $options = []): void {
                 }, 'w',
             ],
 
-            [
+            'insertMany' => [
                 function ($collection, $session, $options = []): void {
                     $collection->insertMany(
                         [
@@ -610,7 +624,7 @@ function ($collection, $session, $options = []): void {
                 }, 'w',
             ],
 
-            [
+            'insertOne' => [
                 function ($collection, $session, $options = []): void {
                     $collection->insertOne(
                         ['test' => 'foo'],
@@ -620,7 +634,7 @@ function ($collection, $session, $options = []): void {
             ],
 
             /* Disabled, as it's illegal to use listIndexes command in transactions
-            [
+            'listIndexes' => [
                 function($collection, $session, $options = []) {
                     $collection->listIndexes(
                         ['session' => $session] + $options
@@ -630,7 +644,7 @@ function($collection, $session, $options = []) {
             */
 
             /* Disabled, as it's illegal to use mapReduce command in transactions
-            [
+            'mapReduce' => [
                 function($collection, $session, $options = []) {
                     $collection->mapReduce(
                         new \MongoDB\BSON\Javascript('function() { emit(this.state, this.pop); }'),
@@ -642,7 +656,7 @@ function($collection, $session, $options = []) {
             ],
             */
 
-            [
+            'replaceOne' => [
                 function ($collection, $session, $options = []): void {
                     $collection->replaceOne(
                         ['test' => 'foo'],
@@ -652,7 +666,7 @@ function ($collection, $session, $options = []): void {
                 }, 'w',
             ],
 
-            [
+            'updateMany' => [
                 function ($collection, $session, $options = []): void {
                     $collection->updateMany(
                         ['test' => 'foo'],
@@ -662,7 +676,7 @@ function ($collection, $session, $options = []): void {
                 }, 'w',
             ],
 
-            [
+            'updateOne' => [
                 function ($collection, $session, $options = []): void {
                     $collection->updateOne(
                         ['test' => 'foo'],
@@ -673,7 +687,7 @@ function ($collection, $session, $options = []): void {
             ],
 
             /* Disabled, as it's illegal to use change streams in transactions
-            [
+            'watch' => [
                 function($collection, $session, $options = []) {
                     $collection->watch(
                         [],
@@ -685,32 +699,28 @@ function($collection, $session, $options = []) {
         ];
     }
 
-    public function collectionReadMethodClosures()
+    public function collectionReadMethodClosures(): array
     {
         return array_filter(
             $this->collectionMethodClosures(),
             function ($rw) {
-                if (strchr($rw[1], 'r') !== false) {
-                    return true;
-                }
+                return str_contains($rw[1], 'r');
             }
         );
     }
 
-    public function collectionWriteMethodClosures()
+    public function collectionWriteMethodClosures(): array
     {
         return array_filter(
             $this->collectionMethodClosures(),
             function ($rw) {
-                if (strchr($rw[1], 'w') !== false) {
-                    return true;
-                }
+                return str_contains($rw[1], 'w');
             }
         );
     }
 
     /** @dataProvider collectionMethodClosures */
-    public function testMethodDoesNotInheritReadWriteConcernInTranasaction(Closure $method): void
+    public function testMethodDoesNotInheritReadWriteConcernInTransaction(Closure $method): void
     {
         $this->skipIfTransactionsAreNotSupported();