diff --git a/pyobas/__init__.py b/pyobas/__init__.py
index c384908..e1a275a 100644
--- a/pyobas/__init__.py
+++ b/pyobas/__init__.py
@@ -1,5 +1,5 @@
 # -*- coding: utf-8 -*-
-__version__ = "4.0.0"
+__version__ = "3.5.1"
 
 from pyobas._version import (  # noqa: F401
     __author__,
diff --git a/pyobas/_version.py b/pyobas/_version.py
index fa1366c..999e672 100644
--- a/pyobas/_version.py
+++ b/pyobas/_version.py
@@ -3,4 +3,4 @@
 __email__ = "contact@filigran.io"
 __license__ = "Apache 2.0"
 __title__ = "python-openbas"
-__version__ = "4.0.0"
+__version__ = "3.5.1"
diff --git a/pyobas/contracts/contract_config.py b/pyobas/contracts/contract_config.py
index 2ca23ab..6a35c55 100644
--- a/pyobas/contracts/contract_config.py
+++ b/pyobas/contracts/contract_config.py
@@ -78,7 +78,7 @@ def __post_init__(self):
 
 @dataclass
 class ContractCardinalityElement(ContractElement, ABC):
-    cardinality: ContractCardinality = ContractCardinality.One
+    cardinality: str = ContractCardinality.One
     defaultValue: List[str] = field(default_factory=list)
 
 
diff --git a/pyobas/helpers.py b/pyobas/helpers.py
index 32ed96f..851bd7c 100644
--- a/pyobas/helpers.py
+++ b/pyobas/helpers.py
@@ -341,7 +341,6 @@ def schedule(self, message_callback, delay):
             self.config_helper.get_conf("collector_id"),
             {"collector_last_execution": now},
         )
-
         # Then schedule the next execution
         self.scheduler.enter(
             delay, 1, self._schedule, (self.scheduler, message_callback, delay)