diff --git a/modoboa/admin/forms/domain.py b/modoboa/admin/forms/domain.py
index 58a5b1f4f..00ac7c962 100644
--- a/modoboa/admin/forms/domain.py
+++ b/modoboa/admin/forms/domain.py
@@ -96,6 +96,13 @@ class DomainFormGeneral(forms.ModelForm, DynamicForm):
                 "name", _("A %s with this name already exists")
                 % unicode(label)
             )
+        condition = (
+            self.cleaned_data["default_mailbox_quota"] >
+            self.cleaned_data["quota"])
+        if condition:
+            self.add_error(
+                "default_mailbox_quota",
+                _("Cannot be greater than domain quota"))
         if self.user.role == "Resellers":
             limit = self.user.userobjectlimit_set.get(name="quota")
             if limit.max_value != 0:
diff --git a/modoboa/admin/models/domain.py b/modoboa/admin/models/domain.py
index 666514796..cfae8f6f3 100644
--- a/modoboa/admin/models/domain.py
+++ b/modoboa/admin/models/domain.py
@@ -265,6 +265,11 @@ class Domain(AdminObject):
                 _("Invalid default mailbox quota value for domain '{}'")
                 .format(self.name)
             )
+        if self.quota != 0 and self.default_mailbox_quota > self.quota:
+            raise BadRequest(
+                _("Default mailbox quota cannot be greater than domain "
+                  "quota")
+            )
         self.enabled = (row[4].strip() in ["True", "1", "yes", "y"])
         core_signals.can_create_object.send(
             sender=self.__class__, context=user, klass=Domain,
diff --git a/modoboa/admin/serializers.py b/modoboa/admin/serializers.py
index 20a4e10fd..3376c73a6 100644
--- a/modoboa/admin/serializers.py
+++ b/modoboa/admin/serializers.py
@@ -27,6 +27,17 @@ class DomainSerializer(serializers.ModelSerializer):
             "pk", "name", "quota", "default_mailbox_quota", "enabled", "type",
         )
 
+    def validate(self, data):
+        """Check quota values."""
+        quota = data["quota"]
+        default_mailbox_quota = data["default_mailbox_quota"]
+        if quota != 0 and default_mailbox_quota > quota:
+            raise serializers.ValidationError({
+                "default_mailbox_quota":
+                _("Cannot be greater than domain quota")
+            })
+        return data
+
     def create(self, validated_data):
         """Set permissions."""
         domain = models.Domain(**validated_data)