diff --git a/classes/Tools.php b/classes/Tools.php
index fa03b884a..b3bcde0b1 100644
--- a/classes/Tools.php
+++ b/classes/Tools.php
@@ -1916,7 +1916,7 @@ FileETag INode MTime Size
 		else
 		{
 			$value_length = strlen($value);
-			$qty = substr($value, 0, $value_length - 1 );
+			$qty = (int)substr($value, 0, $value_length - 1 );
 			$unit = strtolower(substr($value, $value_length - 1));
 			switch ($unit)
 			{
diff --git a/controllers/admin/AdminPreferencesController.php b/controllers/admin/AdminPreferencesController.php
index ed64aa344..1585184fb 100644
--- a/controllers/admin/AdminPreferencesController.php
+++ b/controllers/admin/AdminPreferencesController.php
@@ -385,14 +385,15 @@ class AdminPreferencesControllerCore extends AdminController
 	/**
 	 * Update PS_ATTACHMENT_MAXIMUM_SIZE
 	 */
-	public function updateOptionPsAttachementMaximumSize($value)
+	public function updateOptionPsAttachmentMaximumSize($value)
 	{
 		if (!$value)
 			return;
 
-		$upload_max_size = (int)str_replace('M', '', ini_get('upload_max_filesize'));
-		$post_max_size = (int)str_replace('M', '', ini_get('post_max_size'));
-		$max_size = $upload_max_size < $post_max_size ? $upload_max_size : $post_max_size;
+		$upload_max_size = Tools::convertBytes(ini_get('upload_max_filesize'));
+		$post_max_size = Tools::convertBytes(ini_get('post_max_size'));
+		$max_size = ($upload_max_size < $post_max_size ? $upload_max_size : $post_max_size) / 1048576;
+		// at this point, all values are in megaBytes
 		$value = ($max_size < Tools::getValue('PS_ATTACHMENT_MAXIMUM_SIZE')) ? $max_size : Tools::getValue('PS_ATTACHMENT_MAXIMUM_SIZE');
 		Configuration::update('PS_ATTACHMENT_MAXIMUM_SIZE', $value);
 	}