--- a/src/iconolab/models.py	Mon Sep 19 15:13:16 2016 +0200
+++ b/src/iconolab/models.py	Mon Sep 19 15:27:18 2016 +0200
@@ -84,7 +84,7 @@
     tag_count = models.IntegerField(blank=True, null=True, default=0)
     
     def __str__(self):
-        return "stats:for:"+self.image.image_guid
+        return "stats:for:"+str(self.image.image_guid)
     
     def set_tags_stats(self):
         self.tag_count = Tag.objects.filter(tagginginfo__revision__annotation__image = self.image).distinct().count()