diff --git a/apps/accounts/models/hosting.py b/apps/accounts/models/hosting.py
index 1a8ac8cd..0ea6c5c1 100644
--- a/apps/accounts/models/hosting.py
+++ b/apps/accounts/models/hosting.py
@@ -846,7 +846,7 @@ class Meta:
 
 
 class HostingproviderStats(models.Model):
-    hostingprovider = models.ForeignKey(
+    hostingprovider = models.OneToOneField(
         Hostingprovider,
         on_delete=models.CASCADE,
         db_column="id_hp",
diff --git a/apps/greencheck/models/stats.py b/apps/greencheck/models/stats.py
index 125750ea..e0c682ba 100644
--- a/apps/greencheck/models/stats.py
+++ b/apps/greencheck/models/stats.py
@@ -17,8 +17,12 @@
 
 logger = logging.getLogger(__name__)
 
-now = timezone.now()
-yesterday = now - relativedelta(days=1)
+def yesterday():
+    """Return the the day before today.
+    Used as default value for date fields.
+    """
+    now = timezone.now()
+    return now - relativedelta(days=1)
 
 
 class Stats(models.Model):