diff --git a/CHANGELOG.md b/CHANGELOG.md
index fe6512ccc3..b2eef3140e 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -5,6 +5,7 @@
 - Fixed an SQL error that occurred when duplicating variants. ([#3727](https://github.com/craftcms/commerce/issues/3727))
 - Fixed a PHP error that could occur when completing an order. ([#3733](https://github.com/craftcms/commerce/issues/3733))
 - Fixed a bug where the “Product” navigation item could be missing from the navigation. ([#3735](https://github.com/craftcms/commerce/issues/3735))  
+- Fixed a PHP error that could occur when completing an order. ([#3736](https://github.com/craftcms/commerce/issues/3736))
 
 ## 5.2.0 - 2024-10-16
 
diff --git a/src/controllers/DownloadsController.php b/src/controllers/DownloadsController.php
index 92011c410d..be5685e834 100644
--- a/src/controllers/DownloadsController.php
+++ b/src/controllers/DownloadsController.php
@@ -72,7 +72,7 @@ public function actionPdf(): Response
         $renderedPdf = Plugin::getInstance()->getPdfs()->renderPdfForOrder($order, $option, null, [], $pdf);
 
         // Set previous language back
-        Locale::switchAppLanguage($originalLanguage, $originalFormattingLocale);
+        Locale::switchAppLanguage($originalLanguage, $originalFormattingLocale->id);
 
         $fileName = $this->getView()->renderObjectTemplate((string)$pdf->fileNameFormat, $order);
         if (!$fileName) {
diff --git a/src/controllers/OrdersController.php b/src/controllers/OrdersController.php
index fb61553061..871261b627 100644
--- a/src/controllers/OrdersController.php
+++ b/src/controllers/OrdersController.php
@@ -930,7 +930,7 @@ public function actionSendEmail(): Response
         }
 
         // Set previous language back
-        Locale::switchAppLanguage($originalLanguage, $originalFormattingLocale);
+        Locale::switchAppLanguage($originalLanguage, $originalFormattingLocale->id);
 
         if (!$success) {
             $error = $error ?: Craft::t('commerce', 'Could not send email');
diff --git a/src/queue/jobs/SendEmail.php b/src/queue/jobs/SendEmail.php
index 06750134b3..60ae119a6d 100644
--- a/src/queue/jobs/SendEmail.php
+++ b/src/queue/jobs/SendEmail.php
@@ -76,7 +76,7 @@ public function execute($queue): void
         }
 
         // Set previous language back
-        Locale::switchAppLanguage($originalLanguage, $originalFormattingLocale);
+        Locale::switchAppLanguage($originalLanguage, $originalFormattingLocale->id);
 
         $this->setProgress($queue, 1);
     }
diff --git a/src/services/OrderStatuses.php b/src/services/OrderStatuses.php
index 03a8a7ecec..80c8c864ca 100644
--- a/src/services/OrderStatuses.php
+++ b/src/services/OrderStatuses.php
@@ -502,7 +502,7 @@ public function statusChangeHandler(Order $order, OrderHistory $orderHistory): v
         }
 
         // Set previous language back
-        Locale::switchAppLanguage($originalLanguage, $originalFormattingLocale);
+        Locale::switchAppLanguage($originalLanguage, $originalFormattingLocale->id);
     }
 
     /**
diff --git a/src/services/Pdfs.php b/src/services/Pdfs.php
index 86875b8ab6..444e054dc3 100644
--- a/src/services/Pdfs.php
+++ b/src/services/Pdfs.php
@@ -509,7 +509,7 @@ public function renderPdfForOrder(Order $order, string $option = '', string $tem
         if (!$event->template || !$view->doesTemplateExist($event->template)) {
             // Restore the original template mode
             $view->setTemplateMode($oldTemplateMode);
-            Locale::switchAppLanguage($originalLanguage, $originalFormattingLanguage);
+            Locale::switchAppLanguage($originalLanguage, $originalFormattingLanguage->id);
 
             throw new Exception('PDF template file does not exist.');
         }
@@ -518,14 +518,14 @@ public function renderPdfForOrder(Order $order, string $option = '', string $tem
             // TODO Add event
             $html = $view->renderTemplate($event->template, $variables);
         } catch (\Exception $e) {
-            Locale::switchAppLanguage($originalLanguage, $originalFormattingLanguage);
+            Locale::switchAppLanguage($originalLanguage, $originalFormattingLanguage->id);
             // Set the pdf html to the render error.
             Craft::error('Order PDF render error. Order number: ' . $order->getShortNumber() . '. ' . $e->getMessage());
             Craft::$app->getErrorHandler()->logException($e);
             $html = Craft::t('commerce', 'An error occurred while generating this PDF.');
         }
 
-        Locale::switchAppLanguage($originalLanguage, $originalFormattingLanguage);
+        Locale::switchAppLanguage($originalLanguage, $originalFormattingLanguage->id);
         // Restore the original template mode
         $view->setTemplateMode($oldTemplateMode);