diff --git a/.github/workflows/coding-standards.yml b/.github/workflows/coding-standards.yml
index 9dc3a9a6a9..02dca84361 100644
--- a/.github/workflows/coding-standards.yml
+++ b/.github/workflows/coding-standards.yml
@@ -50,6 +50,11 @@ jobs:
       - name: "Install dependencies with Composer"
         uses: "ramsey/composer-install@v1"
 
+      - name: "Upload composer.lock as build artifact"
+        uses: actions/upload-artifact@v2
+        with:
+          name: composer.lock
+          path: composer.lock
 
       # https://github.com/doctrine/.github/issues/3
       - name: "Run PHP_CodeSniffer"
diff --git a/.github/workflows/continuous-integration.yml b/.github/workflows/continuous-integration.yml
index 88546fb2cd..e495b70cc6 100644
--- a/.github/workflows/continuous-integration.yml
+++ b/.github/workflows/continuous-integration.yml
@@ -12,12 +12,10 @@ env:
 jobs:
   phpunit:
     name: "PHPUnit"
-    runs-on: "${{ matrix.os }}"
+    runs-on: "ubuntu-18.04"
 
     strategy:
       matrix:
-        os:
-          - "ubuntu-18.04"
         php-version:
           - "7.2"
           - "7.3"
@@ -35,13 +33,11 @@ jobs:
           - "highest"
         include:
           - deps: "lowest"
-            os: "ubuntu-16.04"
             php-version: "7.2"
             mongodb-version: "3.6"
             driver-version: "1.5.0"
             topology: "server"
           - topology: "sharded_cluster"
-            os: "ubuntu-18.04"
             php-version: "8.0"
             mongodb-version: "4.4"
             driver-version: "stable"
@@ -86,6 +82,12 @@ jobs:
           dependency-versions: "${{ matrix.dependencies }}"
           composer-options: "--prefer-dist"
 
+      - name: "Upload composer.lock as build artifact"
+        uses: actions/upload-artifact@v2
+        with:
+          name: composer.lock
+          path: composer.lock
+
       - id: setup-mongodb
         uses: mongodb-labs/drivers-evergreen-tools@master
         with:
diff --git a/.github/workflows/performance.yml b/.github/workflows/performance.yml
index 1e9792830b..3f0325a942 100644
--- a/.github/workflows/performance.yml
+++ b/.github/workflows/performance.yml
@@ -54,6 +54,12 @@ jobs:
       - name: "Install dependencies with Composer"
         uses: "ramsey/composer-install@v1"
 
+      - name: "Upload composer.lock as build artifact"
+        uses: actions/upload-artifact@v2
+        with:
+          name: composer.lock
+          path: composer.lock
+
       # https://github.com/doctrine/.github/issues/3
       - name: "Run PHP_CodeSniffer"
         run: "vendor/bin/phpbench run --report=default --revs=100 --iterations=5 --report=aggregate"
diff --git a/.github/workflows/static-analysis.yml b/.github/workflows/static-analysis.yml
index 5109efe477..e0ad865ade 100644
--- a/.github/workflows/static-analysis.yml
+++ b/.github/workflows/static-analysis.yml
@@ -49,6 +49,12 @@ jobs:
       - name: "Install dependencies with Composer"
         uses: "ramsey/composer-install@v1"
 
+      - name: "Upload composer.lock as build artifact"
+        uses: actions/upload-artifact@v2
+        with:
+          name: composer.lock
+          path: composer.lock
+
       - name: "Run a static analysis with phpstan/phpstan"
         run: "vendor/bin/phpstan analyse --error-format=github"
 
@@ -75,5 +81,11 @@ jobs:
       - name: "Install dependencies with Composer"
         uses: "ramsey/composer-install@v1"
 
+      - name: "Upload composer.lock as build artifact"
+        uses: actions/upload-artifact@v2
+        with:
+          name: composer.lock
+          path: composer.lock
+
       - name: "Run a static analysis with vimeo/psalm"
         run: "vendor/bin/psalm --show-info=false --stats --output-format=github --threads=$(nproc) --php-version=${{ matrix.php-version }}"
diff --git a/lib/Doctrine/ODM/MongoDB/Persisters/PersistenceBuilder.php b/lib/Doctrine/ODM/MongoDB/Persisters/PersistenceBuilder.php
index adf1c9ef3b..4d405a1a03 100644
--- a/lib/Doctrine/ODM/MongoDB/Persisters/PersistenceBuilder.php
+++ b/lib/Doctrine/ODM/MongoDB/Persisters/PersistenceBuilder.php
@@ -68,14 +68,11 @@ public function prepareInsertData($document)
         foreach ($class->fieldMappings as $mapping) {
             $new = $changeset[$mapping['fieldName']][1] ?? null;
 
-            if ($new === null && $mapping['nullable']) {
-                $insertData[$mapping['name']] = null;
-            }
-
-            /* Nothing more to do for null values, since we're either storing
-             * them (if nullable was true) or not.
-             */
             if ($new === null) {
+                if ($mapping['nullable']) {
+                    $insertData[$mapping['name']] = null;
+                }
+
                 continue;
             }
 
@@ -143,34 +140,36 @@ public function prepareUpdateData($document)
 
             [$old, $new] = $change;
 
+            if ($new === null) {
+                if ($mapping['nullable'] === true) {
+                    $updateData['$set'][$mapping['name']] = null;
+                } else {
+                    $updateData['$unset'][$mapping['name']] = true;
+                }
+
+                continue;
+            }
+
             // Scalar fields
             if (! isset($mapping['association'])) {
-                if ($new === null && $mapping['nullable'] !== true) {
-                    $updateData['$unset'][$mapping['name']] = true;
+                if (isset($mapping['strategy']) && $mapping['strategy'] === ClassMetadata::STORAGE_STRATEGY_INCREMENT) {
+                    $operator = '$inc';
+                    $type     = Type::getType($mapping['type']);
+                    assert($type instanceof Incrementable);
+                    $value = $type->convertToDatabaseValue($type->diff($old, $new));
                 } else {
-                    if ($new !== null && isset($mapping['strategy']) && $mapping['strategy'] === ClassMetadata::STORAGE_STRATEGY_INCREMENT) {
-                        $operator = '$inc';
-                        $type     = Type::getType($mapping['type']);
-                        assert($type instanceof Incrementable);
-                        $value = $type->convertToDatabaseValue($type->diff($old, $new));
-                    } else {
-                        $operator = '$set';
-                        $value    = $new === null ? null : Type::getType($mapping['type'])->convertToDatabaseValue($new);
-                    }
-
-                    $updateData[$operator][$mapping['name']] = $value;
+                    $operator = '$set';
+                    $value    = Type::getType($mapping['type'])->convertToDatabaseValue($new);
                 }
 
+                $updateData[$operator][$mapping['name']] = $value;
+
             // @EmbedOne
             } elseif (isset($mapping['association']) && $mapping['association'] === ClassMetadata::EMBED_ONE) {
                 // If we have a new embedded document then lets set the whole thing
-                if ($new && $this->uow->isScheduledForInsert($new)) {
+                if ($this->uow->isScheduledForInsert($new)) {
                     $updateData['$set'][$mapping['name']] = $this->prepareEmbeddedDocumentValue($mapping, $new);
 
-                // If we don't have a new value then lets unset the embedded document
-                } elseif (! $new) {
-                    $updateData['$unset'][$mapping['name']] = true;
-
                 // Update existing embedded document
                 } else {
                     $update = $this->prepareUpdateData($new);
@@ -182,7 +181,7 @@ public function prepareUpdateData($document)
                 }
 
             // @ReferenceMany, @EmbedMany
-            } elseif (isset($mapping['association']) && $mapping['type'] === 'many' && $new) {
+            } elseif (isset($mapping['association']) && $mapping['type'] === 'many') {
                 if (CollectionHelper::isAtomic($mapping['strategy']) && $this->uow->isCollectionScheduledForUpdate($new)) {
                     $updateData['$set'][$mapping['name']] = $this->prepareAssociatedCollectionValue($new, true);
                 } elseif (CollectionHelper::isAtomic($mapping['strategy']) && $this->uow->isCollectionScheduledForDeletion($new)) {
@@ -208,11 +207,7 @@ public function prepareUpdateData($document)
 
             // @ReferenceOne
             } elseif (isset($mapping['association']) && $mapping['association'] === ClassMetadata::REFERENCE_ONE) {
-                if (isset($new) || $mapping['nullable'] === true) {
-                    $updateData['$set'][$mapping['name']] = $new === null ? null : $this->prepareReferencedDocumentValue($mapping, $new);
-                } else {
-                    $updateData['$unset'][$mapping['name']] = true;
-                }
+                $updateData['$set'][$mapping['name']] = $this->prepareReferencedDocumentValue($mapping, $new);
             }
         }
 
@@ -250,31 +245,36 @@ public function prepareUpsertData($document)
 
             [$old, $new] = $change;
 
+            // Fields with a null value should only be written for inserts
+            if ($new === null) {
+                if ($mapping['nullable'] === true) {
+                    $updateData['$setOnInsert'][$mapping['name']] = null;
+                }
+
+                continue;
+            }
+
             // Scalar fields
             if (! isset($mapping['association'])) {
-                if ($new !== null) {
-                    if (empty($mapping['id']) && isset($mapping['strategy']) && $mapping['strategy'] === ClassMetadata::STORAGE_STRATEGY_INCREMENT) {
-                        $operator = '$inc';
-                        $type     = Type::getType($mapping['type']);
-                        assert($type instanceof Incrementable);
-                        $value = $type->convertToDatabaseValue($type->diff($old, $new));
-                    } else {
-                        $operator = '$set';
-                        $value    = Type::getType($mapping['type'])->convertToDatabaseValue($new);
-                    }
-
-                    $updateData[$operator][$mapping['name']] = $value;
-                } elseif ($mapping['nullable'] === true) {
-                    $updateData['$setOnInsert'][$mapping['name']] = null;
+                if (empty($mapping['id']) && isset($mapping['strategy']) && $mapping['strategy'] === ClassMetadata::STORAGE_STRATEGY_INCREMENT) {
+                    $operator = '$inc';
+                    $type     = Type::getType($mapping['type']);
+                    assert($type instanceof Incrementable);
+                    $value = $type->convertToDatabaseValue($type->diff($old, $new));
+                } else {
+                    $operator = '$set';
+                    $value    = Type::getType($mapping['type'])->convertToDatabaseValue($new);
                 }
 
+                $updateData[$operator][$mapping['name']] = $value;
+
             // @EmbedOne
             } elseif (isset($mapping['association']) && $mapping['association'] === ClassMetadata::EMBED_ONE) {
                 // If we don't have a new value then do nothing on upsert
                 // If we have a new embedded document then lets set the whole thing
-                if ($new && $this->uow->isScheduledForInsert($new)) {
+                if ($this->uow->isScheduledForInsert($new)) {
                     $updateData['$set'][$mapping['name']] = $this->prepareEmbeddedDocumentValue($mapping, $new);
-                } elseif ($new) {
+                } else {
                     // Update existing embedded document
                     $update = $this->prepareUpsertData($new);
                     foreach ($update as $cmd => $values) {
@@ -286,9 +286,7 @@ public function prepareUpsertData($document)
 
             // @ReferenceOne
             } elseif (isset($mapping['association']) && $mapping['association'] === ClassMetadata::REFERENCE_ONE) {
-                if (isset($new) || $mapping['nullable'] === true) {
-                    $updateData['$set'][$mapping['name']] = $new === null ? null : $this->prepareReferencedDocumentValue($mapping, $new);
-                }
+                $updateData['$set'][$mapping['name']] = $this->prepareReferencedDocumentValue($mapping, $new);
 
             // @ReferenceMany, @EmbedMany
             } elseif (
diff --git a/lib/Doctrine/ODM/MongoDB/Query/Builder.php b/lib/Doctrine/ODM/MongoDB/Query/Builder.php
index a800303a58..2c959178ce 100644
--- a/lib/Doctrine/ODM/MongoDB/Query/Builder.php
+++ b/lib/Doctrine/ODM/MongoDB/Query/Builder.php
@@ -1028,11 +1028,11 @@ public function nearSphere($x, $y = null): self
      * @see Expr::not()
      * @see https://docs.mongodb.com/manual/reference/operator/not/
      *
-     * @param array|Expr $expression
+     * @param array|Expr|mixed $valueOrExpression
      */
-    public function not($expression): self
+    public function not($valueOrExpression): self
     {
-        $this->expr->not($expression);
+        $this->expr->not($valueOrExpression);
 
         return $this;
     }
diff --git a/lib/Doctrine/ODM/MongoDB/Query/Expr.php b/lib/Doctrine/ODM/MongoDB/Query/Expr.php
index e924a66fc8..86e47f4dfd 100644
--- a/lib/Doctrine/ODM/MongoDB/Query/Expr.php
+++ b/lib/Doctrine/ODM/MongoDB/Query/Expr.php
@@ -861,11 +861,11 @@ public function nearSphere($x, $y = null): self
      * @see Builder::not()
      * @see https://docs.mongodb.com/manual/reference/operator/not/
      *
-     * @param array|Expr $expression
+     * @param array|Expr|mixed $valueOrExpression
      */
-    public function not($expression): self
+    public function not($valueOrExpression): self
     {
-        return $this->operator('$not', $expression);
+        return $this->operator('$not', $valueOrExpression);
     }
 
     /**
diff --git a/lib/Doctrine/ODM/MongoDB/UnitOfWork.php b/lib/Doctrine/ODM/MongoDB/UnitOfWork.php
index 7b539a3631..428ad52a0b 100644
--- a/lib/Doctrine/ODM/MongoDB/UnitOfWork.php
+++ b/lib/Doctrine/ODM/MongoDB/UnitOfWork.php
@@ -1459,6 +1459,10 @@ public function scheduleForDelete(object $document, bool $isView = false): void
             unset($this->documentUpdates[$oid]);
         }
 
+        if (isset($this->documentUpserts[$oid])) {
+            unset($this->documentUpserts[$oid]);
+        }
+
         if (isset($this->documentDeletions[$oid])) {
             return;
         }
diff --git a/phpstan-baseline.neon b/phpstan-baseline.neon
index c308c9d739..9a8ee72c32 100644
--- a/phpstan-baseline.neon
+++ b/phpstan-baseline.neon
@@ -9,9 +9,8 @@ parameters:
         # Making classes final as suggested would be a BC-break
         -
             message: "#^Unsafe usage of new static\\(\\)\\.$#"
-            paths:
-                 - lib/Doctrine/ODM/MongoDB/Aggregation/Expr.php
-                 - lib/Doctrine/ODM/MongoDB/DocumentManager.php
+            count: 1
+            path: lib/Doctrine/ODM/MongoDB/Aggregation/Expr.php
 
         # This cannot be solved the way it is, see https://github.com/vimeo/psalm/issues/5788
         -
@@ -25,6 +24,24 @@ parameters:
             count: 1
             path: lib/Doctrine/ODM/MongoDB/Aggregation/Stage/GeoNear.php
 
+        # Fixed in 2.3
+        -
+            message: "#^Method Doctrine\\\\ODM\\\\MongoDB\\\\DocumentManager\\:\\:find\\(\\) should return T of object\\|null but returns object\\|null\\.$#"
+            count: 1
+            path: lib/Doctrine/ODM/MongoDB/DocumentManager.php
+
+        # Fixed in 2.3
+        -
+            message: "#^Return type \\(Doctrine\\\\ODM\\\\MongoDB\\\\Mapping\\\\ClassMetadataFactory\\) of method Doctrine\\\\ODM\\\\MongoDB\\\\DocumentManager\\:\\:getMetadataFactory\\(\\) should be compatible with return type \\(Doctrine\\\\Persistence\\\\Mapping\\\\ClassMetadataFactory\\<Doctrine\\\\Persistence\\\\Mapping\\\\ClassMetadata\\<object\\>\\>\\) of method Doctrine\\\\Persistence\\\\ObjectManager\\:\\:getMetadataFactory\\(\\)$#"
+            count: 1
+            path: lib/Doctrine/ODM/MongoDB/DocumentManager.php
+
+        # Making classes final as suggested would be a BC-break
+        -
+            message: "#^Unsafe usage of new static\\(\\)\\.$#"
+            count: 1
+            path: lib/Doctrine/ODM/MongoDB/DocumentManager.php
+
         # Union types cannot be added yet
         -
             message: "#^Result of && is always false\\.$#"
diff --git a/psalm-baseline.xml b/psalm-baseline.xml
new file mode 100644
index 0000000000..8e22801a5e
--- /dev/null
+++ b/psalm-baseline.xml
@@ -0,0 +1,31 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<files psalm-version="4.7.3@38c452ae584467e939d55377aaf83b5a26f19dd1">
+  <file src="lib/Doctrine/ODM/MongoDB/DocumentManager.php">
+    <ParamNameMismatch occurrences="8">
+      <code>$document</code>
+      <code>$document</code>
+      <code>$document</code>
+      <code>$document</code>
+      <code>$document</code>
+      <code>$document</code>
+      <code>$documentName</code>
+      <code>$documentName</code>
+    </ParamNameMismatch>
+  </file>
+  <file src="lib/Doctrine/ODM/MongoDB/Mapping/ClassMetadata.php">
+    <ParamNameMismatch occurrences="2">
+      <code>$fieldName</code>
+      <code>$fieldName</code>
+    </ParamNameMismatch>
+  </file>
+  <file src="lib/Doctrine/ODM/MongoDB/PersistentCollection/PersistentCollectionTrait.php">
+    <ParamNameMismatch occurrences="1">
+      <code>$value</code>
+    </ParamNameMismatch>
+  </file>
+  <file src="lib/Doctrine/ODM/MongoDB/Query/QueryExpressionVisitor.php">
+    <ParamNameMismatch occurrences="1">
+      <code>$compositeExpr</code>
+    </ParamNameMismatch>
+  </file>
+</files>
diff --git a/psalm.xml b/psalm.xml
index 0fdfeb3390..bbb07a611e 100644
--- a/psalm.xml
+++ b/psalm.xml
@@ -6,6 +6,7 @@
     xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
     xmlns="https://getpsalm.org/schema/config"
     xsi:schemaLocation="https://getpsalm.org/schema/config vendor/vimeo/psalm/config.xsd"
+    errorBaseline="psalm-baseline.xml"
 >
     <projectFiles>
         <directory name="lib/Doctrine/ODM/MongoDB" />
diff --git a/tests/Doctrine/ODM/MongoDB/Tests/Functional/EmbeddedTest.php b/tests/Doctrine/ODM/MongoDB/Tests/Functional/EmbeddedTest.php
index 8e1b9b54b8..d9e82a5e5e 100644
--- a/tests/Doctrine/ODM/MongoDB/Tests/Functional/EmbeddedTest.php
+++ b/tests/Doctrine/ODM/MongoDB/Tests/Functional/EmbeddedTest.php
@@ -431,6 +431,7 @@ public function testRemoveEmbeddedDocument()
 
         $check = $this->dm->getDocumentCollection(User::class)->findOne();
         $this->assertEmpty($check['phonenumbers']);
+        $this->assertNull($check['addressNullable']);
         $this->assertArrayNotHasKey('address', $check);
     }
 
diff --git a/tests/Doctrine/ODM/MongoDB/Tests/Functional/QueryTest.php b/tests/Doctrine/ODM/MongoDB/Tests/Functional/QueryTest.php
index cc7532a389..d9af374376 100644
--- a/tests/Doctrine/ODM/MongoDB/Tests/Functional/QueryTest.php
+++ b/tests/Doctrine/ODM/MongoDB/Tests/Functional/QueryTest.php
@@ -15,6 +15,7 @@
 use InvalidArgumentException;
 use IteratorAggregate;
 use MongoDB\BSON\ObjectId;
+use MongoDB\BSON\Regex;
 use MongoDB\BSON\UTCDateTime;
 
 use function array_values;
@@ -100,6 +101,27 @@ public function testAddNot()
         $this->assertNotNull($user);
     }
 
+    public function testNotAllowsRegex()
+    {
+        $user = new User();
+        $user->setUsername('boo');
+
+        $this->dm->persist($user);
+        $this->dm->flush();
+
+        $qb = $this->dm->createQueryBuilder(User::class);
+        $qb->field('username')->not(new Regex('Boo', 'i'));
+        $query = $qb->getQuery();
+        $user  = $query->getSingleResult();
+        $this->assertNull($user);
+
+        $qb = $this->dm->createQueryBuilder(User::class);
+        $qb->field('username')->not(new Regex('Boo'));
+        $query = $qb->getQuery();
+        $user  = $query->getSingleResult();
+        $this->assertNotNull($user);
+    }
+
     public function testDistinct()
     {
         $user = new User();
diff --git a/tests/Doctrine/ODM/MongoDB/Tests/Functional/Ticket/GH2310Test.php b/tests/Doctrine/ODM/MongoDB/Tests/Functional/Ticket/GH2310Test.php
new file mode 100644
index 0000000000..e00301c8a3
--- /dev/null
+++ b/tests/Doctrine/ODM/MongoDB/Tests/Functional/Ticket/GH2310Test.php
@@ -0,0 +1,124 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Doctrine\ODM\MongoDB\Tests\Functional\Ticket;
+
+use Doctrine\ODM\MongoDB\Tests\BaseTest;
+use Documents74\GH2310Container;
+use Documents74\GH2310Embedded;
+use MongoDB\BSON\ObjectId;
+
+use function phpversion;
+use function version_compare;
+
+class GH2310Test extends BaseTest
+{
+    public function setUp(): void
+    {
+        if (version_compare((string) phpversion(), '7.4.0', '<')) {
+            self::markTestSkipped('PHP 7.4 is required to run this test');
+        }
+
+        parent::setUp();
+    }
+
+    public function testFindWithNullableEmbeddedAfterUpsert(): void
+    {
+        $document = new GH2310Container((string) new ObjectId(), null);
+        $this->dm->persist($document);
+        $this->dm->flush();
+        $this->dm->clear();
+
+        $repository = $this->dm->getRepository(GH2310Container::class);
+        $result     = $repository->find($document->id);
+
+        self::assertInstanceOf(GH2310Container::class, $result);
+        self::assertSame($document->id, $result->id);
+        self::assertNull($result->embedded);
+    }
+
+    public function testAggregatorBuilderWithNullableEmbeddedAfterUpsert(): void
+    {
+        $document = new GH2310Container((string) new ObjectId(), null);
+        $this->dm->persist($document);
+        $this->dm->flush();
+        $this->dm->clear();
+
+        $aggBuilder = $this->dm->createAggregationBuilder(GH2310Container::class);
+        $aggBuilder->match()->field('id')->equals($document->id);
+        $result = $aggBuilder->hydrate(GH2310Container::class)->getAggregation()->getIterator()->current();
+
+        self::assertInstanceOf(GH2310Container::class, $result);
+        self::assertSame($document->id, $result->id);
+        self::assertNull($result->embedded);
+    }
+
+    public function testFindWithNullableEmbeddedAfterInsert(): void
+    {
+        $document = new GH2310Container(null, null);
+        $this->dm->persist($document);
+        $this->dm->flush();
+
+        $repository = $this->dm->getRepository(GH2310Container::class);
+        $result     = $repository->find($document->id);
+
+        self::assertInstanceOf(GH2310Container::class, $result);
+        self::assertSame($document->id, $result->id);
+        self::assertNull($result->embedded);
+    }
+
+    public function testAggregatorBuilderWithNullableEmbeddedAfterInsert(): void
+    {
+        $document = new GH2310Container(null, null);
+        $this->dm->persist($document);
+        $this->dm->flush();
+
+        $aggBuilder = $this->dm->createAggregationBuilder(GH2310Container::class);
+        $aggBuilder->match()->field('id')->equals($document->id);
+        $result = $aggBuilder->hydrate(GH2310Container::class)->getAggregation()->getIterator()->current();
+
+        self::assertInstanceOf(GH2310Container::class, $result);
+        self::assertSame($document->id, $result->id);
+        self::assertNull($result->embedded);
+    }
+
+    public function testFindWithNullableEmbeddedAfterUpdate(): void
+    {
+        $document = new GH2310Container(null, new GH2310Embedded());
+        $this->dm->persist($document);
+        $this->dm->flush();
+
+        // Update embedded document to trigger nullable behaviour
+        $document->embedded = null;
+        $this->dm->flush();
+        $this->dm->clear();
+
+        $repository = $this->dm->getRepository(GH2310Container::class);
+        $result     = $repository->find($document->id);
+
+        self::assertInstanceOf(GH2310Container::class, $result);
+        self::assertSame($document->id, $result->id);
+        self::assertNull($result->embedded);
+    }
+
+    public function testAggregatorBuilderWithNullableEmbeddedAfterUpdate(): void
+    {
+        $document = new GH2310Container(null, new GH2310Embedded());
+        $this->dm->persist($document);
+        $this->dm->flush();
+
+        // Update embedded document to trigger nullable behaviour
+        $document->embedded = null;
+        $this->dm->flush();
+        $this->dm->clear();
+
+        $aggBuilder = $this->dm->createAggregationBuilder(GH2310Container::class);
+        $aggBuilder->match()->field('id')->equals($document->id);
+        $result = $aggBuilder->hydrate(GH2310Container::class)->getAggregation()->getIterator()->current();
+
+        self::assertInstanceOf(GH2310Container::class, $result);
+        self::assertSame($document->id, $result->id);
+        self::assertNull($result->embedded);
+    }
+}
diff --git a/tests/Doctrine/ODM/MongoDB/Tests/Functional/UpsertTest.php b/tests/Doctrine/ODM/MongoDB/Tests/Functional/UpsertTest.php
index 3449292ff7..dbbc148450 100644
--- a/tests/Doctrine/ODM/MongoDB/Tests/Functional/UpsertTest.php
+++ b/tests/Doctrine/ODM/MongoDB/Tests/Functional/UpsertTest.php
@@ -8,6 +8,8 @@
 use Doctrine\ODM\MongoDB\Tests\BaseTest;
 use MongoDB\BSON\ObjectId;
 
+use function assert;
+
 class UpsertTest extends BaseTest
 {
     /**
@@ -17,11 +19,9 @@ class UpsertTest extends BaseTest
      */
     public function testUpsertEmbedManyDoesNotCreateObject()
     {
-        $test     = new UpsertTestUser();
-        $test->id = (string) new ObjectId();
+        $test = new UpsertTestUser();
 
         $embedded       = new UpsertTestUserEmbedded();
-        $embedded->id   = (string) new ObjectId();
         $embedded->test = 'test';
 
         $test->embedMany[] = $embedded;
@@ -36,6 +36,54 @@ public function testUpsertEmbedManyDoesNotCreateObject()
 
         $this->dm->flush();
     }
+
+    public function testUpsertDoesNotOverwriteNullableFieldsOnNull()
+    {
+        $test = new UpsertTestUser();
+
+        $test->nullableField        = 'value';
+        $test->nullableReferenceOne = new UpsertTestUser();
+        $test->nullableEmbedOne     = new UpsertTestUserEmbedded();
+
+        $this->dm->persist($test);
+        $this->dm->flush();
+        $this->dm->clear();
+
+        $upsert = new UpsertTestUser();
+
+        // Re-use old ID but don't set any other values
+        $upsert->id = $test->id;
+
+        $this->dm->persist($upsert);
+        $this->dm->flush();
+        $this->dm->clear();
+
+        $upsertResult = $this->dm->find(UpsertTestUser::class, $test->id);
+        assert($upsertResult instanceof $upsertResult);
+        self::assertNotNull($upsertResult->nullableField);
+        self::assertNotNull($upsertResult->nullableReferenceOne);
+        self::assertNotNull($upsertResult->nullableEmbedOne);
+    }
+
+    public function testUpsertsWritesNullableFieldsOnInsert()
+    {
+        $test = new UpsertTestUser();
+        $this->dm->persist($test);
+        $this->dm->flush();
+
+        $collection = $this->dm->getDocumentCollection(UpsertTestUser::class);
+        $result     = $collection->findOne(['_id' => new ObjectId($test->id)]);
+
+        self::assertEquals(
+            [
+                '_id' => new ObjectId($test->id),
+                'nullableField' => null,
+                'nullableReferenceOne' => null,
+                'nullableEmbedOne' => null,
+            ],
+            $result
+        );
+    }
 }
 
 /** @ODM\Document */
@@ -44,16 +92,27 @@ class UpsertTestUser
     /** @ODM\Id */
     public $id;
 
+    /** @ODM\Field(nullable=true) */
+    public $nullableField;
+
+    /** @ODM\EmbedOne(targetDocument=UpsertTestUserEmbedded::class, nullable=true) */
+    public $nullableEmbedOne;
+
+    /** @ODM\ReferenceOne(targetDocument=UpsertTestUser::class, cascade="persist", nullable=true) */
+    public $nullableReferenceOne;
+
     /** @ODM\EmbedMany(targetDocument=UpsertTestUserEmbedded::class) */
     public $embedMany;
+
+    public function __construct()
+    {
+        $this->id = (string) new ObjectId();
+    }
 }
 
 /** @ODM\EmbeddedDocument */
 class UpsertTestUserEmbedded
 {
-    /** @ODM\Id */
-    public $id;
-
     /** @ODM\Field(type="string") */
     public $test;
 }
diff --git a/tests/Doctrine/ODM/MongoDB/Tests/Query/BuilderTest.php b/tests/Doctrine/ODM/MongoDB/Tests/Query/BuilderTest.php
index 9a644634ef..25420c34be 100644
--- a/tests/Doctrine/ODM/MongoDB/Tests/Query/BuilderTest.php
+++ b/tests/Doctrine/ODM/MongoDB/Tests/Query/BuilderTest.php
@@ -19,6 +19,7 @@
 use InvalidArgumentException;
 use IteratorAggregate;
 use MongoDB\BSON\ObjectId;
+use MongoDB\BSON\Regex;
 use MongoDB\Driver\ReadPreference;
 use ReflectionProperty;
 
@@ -299,6 +300,19 @@ public function testAddNot()
         $this->assertEquals($expected, $qb->getQueryArray());
     }
 
+    public function testNotAllowsRegex()
+    {
+        $qb = $this->getTestQueryBuilder();
+        $qb->field('username')->not(new Regex('Boo', 'i'));
+
+        $expected = [
+            'username' => [
+                '$not' => new Regex('Boo', 'i'),
+            ],
+        ];
+        $this->assertEquals($expected, $qb->getQueryArray());
+    }
+
     public function testFindQuery()
     {
         $qb       = $this->getTestQueryBuilder()
diff --git a/tests/Doctrine/ODM/MongoDB/Tests/UnitOfWorkTest.php b/tests/Doctrine/ODM/MongoDB/Tests/UnitOfWorkTest.php
index 5e5f3bd312..081058422f 100644
--- a/tests/Doctrine/ODM/MongoDB/Tests/UnitOfWorkTest.php
+++ b/tests/Doctrine/ODM/MongoDB/Tests/UnitOfWorkTest.php
@@ -116,6 +116,24 @@ public function testRegisterRemovedOnNewEntityIsIgnored()
         $this->assertFalse($this->uow->isScheduledForDelete($user));
     }
 
+    public function testScheduleForDeleteShouldUnregisterScheduledUpserts()
+    {
+        $class    = $this->dm->getClassMetadata(ForumUser::class);
+        $user     = new ForumUser();
+        $user->id = new ObjectId();
+        $this->assertFalse($this->uow->isScheduledForInsert($user));
+        $this->assertFalse($this->uow->isScheduledForUpsert($user));
+        $this->assertFalse($this->uow->isScheduledForDelete($user));
+        $this->uow->scheduleForUpsert($class, $user);
+        $this->assertFalse($this->uow->isScheduledForInsert($user));
+        $this->assertTrue($this->uow->isScheduledForUpsert($user));
+        $this->assertFalse($this->uow->isScheduledForDelete($user));
+        $this->uow->scheduleForDelete($user);
+        $this->assertFalse($this->uow->isScheduledForInsert($user));
+        $this->assertFalse($this->uow->isScheduledForUpsert($user));
+        $this->assertTrue($this->uow->isScheduledForDelete($user));
+    }
+
     public function testThrowsOnPersistOfMappedSuperclass()
     {
         $this->expectException(MongoDBException::class);
diff --git a/tests/Documents/User.php b/tests/Documents/User.php
index a7de6df61c..688acfdc8f 100644
--- a/tests/Documents/User.php
+++ b/tests/Documents/User.php
@@ -28,9 +28,12 @@ class User extends BaseDocument
     /** @ODM\Field(type="date") */
     protected $createdAt;
 
-    /** @ODM\EmbedOne(targetDocument=Address::class, nullable=true) */
+    /** @ODM\EmbedOne(targetDocument=Address::class) */
     protected $address;
 
+    /** @ODM\EmbedOne(targetDocument=Address::class, nullable=true) */
+    protected $addressNullable;
+
     /** @ODM\ReferenceOne(targetDocument=Profile::class, cascade={"all"}) */
     protected $profile;
 
@@ -181,12 +184,14 @@ public function getAddress()
 
     public function setAddress(?Address $address = null)
     {
-        $this->address = $address;
+        $this->address         = $address;
+        $this->addressNullable = $address ? clone $address : $address;
     }
 
     public function removeAddress()
     {
-        $this->address = null;
+        $this->address         = null;
+        $this->addressNullable = null;
     }
 
     public function setProfile(Profile $profile)
diff --git a/tests/Documents74/GH2310Container.php b/tests/Documents74/GH2310Container.php
new file mode 100644
index 0000000000..bfa5c7fa23
--- /dev/null
+++ b/tests/Documents74/GH2310Container.php
@@ -0,0 +1,34 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Documents74;
+
+use Doctrine\ODM\MongoDB\Mapping\Annotations as ODM;
+
+/**
+ * @ODM\Document()
+ */
+class GH2310Container
+{
+    /** @ODM\Id */
+    public ?string $id;
+
+    /** @ODM\EmbedOne(targetDocument=GH2310Embedded::class, nullable=true) */
+    public ?GH2310Embedded $embedded;
+
+    public function __construct(?string $id, ?GH2310Embedded $embedded)
+    {
+        $this->id       = $id;
+        $this->embedded = $embedded;
+    }
+}
+
+/**
+ * @ODM\EmbeddedDocument
+ */
+class GH2310Embedded
+{
+    /** @ODM\Field(type="integer") */
+    public int $value;
+}