diff --git a/addons/website_slides/models/slide_slide.py b/addons/website_slides/models/slide_slide.py
index 0c6e26dc7e8..29ff814536d 100644
--- a/addons/website_slides/models/slide_slide.py
+++ b/addons/website_slides/models/slide_slide.py
@@ -265,7 +265,7 @@ class Slide(models.Model):
         # Do not use dict.fromkeys(self.ids, dict()) otherwise it will use the same dictionnary for all keys.
         # Therefore, when updating the dict of one key, it updates the dict of all keys.
         keys = ['nbr_%s' % slide_type for slide_type in self.env['slide.slide']._fields['slide_type'].get_values(self.env)]
-        default_vals = dict((key, 0) for key in keys)
+        default_vals = dict((key, 0) for key in keys + ['total_slides'])
 
         res = self.env['slide.slide'].read_group(
             [('is_published', '=', True), ('category_id', 'in', self.ids), ('is_category', '=', False)],