diff --git a/src/applications/auth/engine/PhabricatorAuthSessionEngine.php b/src/applications/auth/engine/PhabricatorAuthSessionEngine.php
--- a/src/applications/auth/engine/PhabricatorAuthSessionEngine.php
+++ b/src/applications/auth/engine/PhabricatorAuthSessionEngine.php
@@ -334,7 +334,7 @@
    */
   public function terminateLoginSessions(
     PhabricatorUser $user,
-    PhutilOpaqueEnvelope $except_session = null) {
+    ?PhutilOpaqueEnvelope $except_session = null) {
 
     $sessions = id(new PhabricatorAuthSessionQuery())
       ->setViewer($user)
@@ -955,7 +955,7 @@
    */
   public function getOneTimeLoginURI(
     PhabricatorUser $user,
-    PhabricatorUserEmail $email = null,
+    ?PhabricatorUserEmail $email = null,
     $type = self::ONETIME_RESET,
     $force_full_session = false) {
 
@@ -1002,7 +1002,7 @@
    */
   public function loadOneTimeLoginKey(
     PhabricatorUser $user,
-    PhabricatorUserEmail $email = null,
+    ?PhabricatorUserEmail $email = null,
     $key = null) {
 
     $key_hash = $this->getOneTimeLoginKeyHash($user, $email, $key);
@@ -1030,7 +1030,7 @@
    */
   private function getOneTimeLoginKeyHash(
     PhabricatorUser $user,
-    PhabricatorUserEmail $email = null,
+    ?PhabricatorUserEmail $email = null,
     $key = null) {
 
     $parts = array(
diff --git a/src/applications/files/storage/PhabricatorFile.php b/src/applications/files/storage/PhabricatorFile.php
--- a/src/applications/files/storage/PhabricatorFile.php
+++ b/src/applications/files/storage/PhabricatorFile.php
@@ -1317,7 +1317,7 @@
     return $this->assertAttached($this->originalFile);
   }
 
-  public function attachOriginalFile(PhabricatorFile $file = null) {
+  public function attachOriginalFile(?PhabricatorFile $file = null) {
     $this->originalFile = $file;
     return $this;
   }
diff --git a/src/applications/project/controller/PhabricatorProjectController.php b/src/applications/project/controller/PhabricatorProjectController.php
--- a/src/applications/project/controller/PhabricatorProjectController.php
+++ b/src/applications/project/controller/PhabricatorProjectController.php
@@ -170,7 +170,7 @@
   protected function newCardResponse(
     $board_phid,
     $object_phid,
-    PhabricatorProjectColumnOrder $ordering = null,
+    ?PhabricatorProjectColumnOrder $ordering = null,
     $sounds = array()) {
 
     $viewer = $this->getViewer();
diff --git a/src/applications/repository/storage/PhabricatorRepository.php b/src/applications/repository/storage/PhabricatorRepository.php
--- a/src/applications/repository/storage/PhabricatorRepository.php
+++ b/src/applications/repository/storage/PhabricatorRepository.php
@@ -250,7 +250,7 @@
   }
 
   public function attachMostRecentCommit(
-    PhabricatorRepositoryCommit $commit = null) {
+    ?PhabricatorRepositoryCommit $commit = null) {
     $this->mostRecentCommit = $commit;
     return $this;
   }
diff --git a/src/applications/search/engine/PhabricatorProfileMenuItemViewList.php b/src/applications/search/engine/PhabricatorProfileMenuItemViewList.php
--- a/src/applications/search/engine/PhabricatorProfileMenuItemViewList.php
+++ b/src/applications/search/engine/PhabricatorProfileMenuItemViewList.php
@@ -171,7 +171,7 @@
 
   private function getHighlightedItemKey(
     array $items,
-    PHUIListItemView $selected_item = null) {
+    ?PHUIListItemView $selected_item = null) {
 
     assert_instances_of($items, 'PHUIListItemView');
 
diff --git a/src/applications/transactions/editor/PhabricatorApplicationTransactionEditor.php b/src/applications/transactions/editor/PhabricatorApplicationTransactionEditor.php
--- a/src/applications/transactions/editor/PhabricatorApplicationTransactionEditor.php
+++ b/src/applications/transactions/editor/PhabricatorApplicationTransactionEditor.php
@@ -5026,7 +5026,7 @@
   }
 
   final protected function newSubEditor(
-    PhabricatorApplicationTransactionEditor $template = null) {
+    ?PhabricatorApplicationTransactionEditor $template = null) {
     $editor = $this->newEditorCopy($template);
 
     $editor->parentEditor = $this;
@@ -5036,7 +5036,7 @@
   }
 
   private function newEditorCopy(
-    PhabricatorApplicationTransactionEditor $template = null) {
+    ?PhabricatorApplicationTransactionEditor $template = null) {
     if ($template === null) {
       $template = newv(get_class($this), array());
     }
diff --git a/src/applications/transactions/error/PhabricatorApplicationTransactionValidationError.php b/src/applications/transactions/error/PhabricatorApplicationTransactionValidationError.php
--- a/src/applications/transactions/error/PhabricatorApplicationTransactionValidationError.php
+++ b/src/applications/transactions/error/PhabricatorApplicationTransactionValidationError.php
@@ -13,7 +13,7 @@
     $type,
     $short_message,
     $message,
-    PhabricatorApplicationTransaction $xaction = null) {
+    ?PhabricatorApplicationTransaction $xaction = null) {
 
     $this->type = $type;
     $this->shortMessage = $short_message;
diff --git a/src/view/page/menu/PhabricatorMainMenuSearchView.php b/src/view/page/menu/PhabricatorMainMenuSearchView.php
--- a/src/view/page/menu/PhabricatorMainMenuSearchView.php
+++ b/src/view/page/menu/PhabricatorMainMenuSearchView.php
@@ -118,7 +118,7 @@
 
   public static function getGlobalSearchScopeItems(
     PhabricatorUser $viewer,
-    PhabricatorApplication $application = null,
+    ?PhabricatorApplication $application = null,
     $global_only = false) {
 
     $items = array();