diff --git a/inc/image.php b/inc/image.php
index 34283b80..20fcfdcb 100644
--- a/inc/image.php
+++ b/inc/image.php
@@ -312,7 +312,7 @@ class ImageConvert extends ImageBase {
 			$this->destroy();
 		}
 		
-		$this->temp = tempnam($config['tmp'], 'convert');
+		$this->temp = tempnam($config['tmp'], 'convert') . ($config['thumb_ext'] == '' ? '' : '.' . $config['thumb_ext']);
 				
 		$config['thumb_keep_animation_frames'] = (int)$config['thumb_keep_animation_frames'];