diff --git a/modoboa/extensions/admin/__init__.py b/modoboa/extensions/admin/__init__.py
index a0f29e83b..12baf0961 100644
--- a/modoboa/extensions/admin/__init__.py
+++ b/modoboa/extensions/admin/__init__.py
@@ -153,7 +153,7 @@ def import_account_mailbox(user, account, row):
     :param list rom: list of fields (strings)
     """
     account.email = row[0].strip()
-    if account.email != "":
+    if account.email:
         account.save()
         mailbox, domname = split_mailbox(account.email)
         try:
@@ -169,8 +169,16 @@ def import_account_mailbox(user, account, row):
         except Mailbox.DoesNotExist:
             pass
         else:
-            raise Conflict(_("Mailbox %s already exists" % account.email))
-        quota = int(row[1].strip())
+            raise  Conflict(_("Mailbox %s already exists" % account.email))
+        if len(row) == 1:
+            quota = None
+        else:
+            try:
+                quota = int(row[1].strip())
+            except ValueError:
+                raise BadRequest(
+                    _("Account import failed (%s): wrong quota value" % account.username)
+                )
         use_domain_quota = True if not quota else False
         mb = Mailbox(address=mailbox, domain=domain,
                      user=account, use_domain_quota=use_domain_quota)
diff --git a/modoboa/extensions/admin/tests/import_.py b/modoboa/extensions/admin/tests/import_.py
index 8f02fed99..7d2c600d7 100644
--- a/modoboa/extensions/admin/tests/import_.py
+++ b/modoboa/extensions/admin/tests/import_.py
@@ -104,6 +104,16 @@ dlist; dlist@test.com; True; user1@test.com; user@extdomain.com
         self.assertTrue(admin.is_owner(dlist))
 
     def test_import_invalid_quota(self):
+        f = ContentFile(b"""
+account; user1@test.com; toto; User; One; True; SimpleUsers; user1@test.com; ; test.com
+""", name="identities.csv")
+        resp = self.clt.post(
+            reverse("modoboa.extensions.admin.views.import.import_identities"),
+            {"sourcefile": f, "crypt_password": True}
+        )
+        self.assertIn('wrong quota value', resp.content)
+
+    def test_import_quota_too_big(self):
         self.clt.logout()
         self.clt.login(username="admin@test.com", password="toto")
         f = ContentFile(b"""
@@ -115,6 +125,20 @@ account; user1@test.com; toto; User; One; True; SimpleUsers; user1@test.com; 20
         )
         self.assertIn('Quota is greater than the allowed', resp.content)
 
+    def test_import_missing_quota(self):
+        f = ContentFile(b"""
+account; user1@test.com; toto; User; One; True; SimpleUsers; user1@test.com
+""", name="identities.csv")
+        resp = self.clt.post(
+            reverse("modoboa.extensions.admin.views.import.import_identities"),
+            {"sourcefile": f, "crypt_password": True}
+        )
+        account = User.objects.get(username="user1@test.com")
+        self.assertEqual(
+            account.mailbox_set.all()[0].quota,
+            account.mailbox_set.all()[0].domain.quota
+        )
+
     def test_import_duplicate(self):
         f = ContentFile(b"""
 account; admin@test.com; toto; Admin; ; True; DomainAdmins; admin@test.com; 0; test.com