diff --git a/src/face_detection.h b/src/face_detection.h
index aaeb2fd..a95667e 100644
--- a/src/face_detection.h
+++ b/src/face_detection.h
@@ -7,6 +7,7 @@
 
 ZEND_BEGIN_ARG_INFO_EX(dlib_face_detection_arginfo, 0, 0, 1)
     ZEND_ARG_INFO(0, img_path)
+    ZEND_ARG_INFO(0, upsample_num)
 ZEND_END_ARG_INFO()
 PHP_FUNCTION(dlib_face_detection);