diff --git a/README.md b/README.md
index d5ba68e..72bebc0 100644
--- a/README.md
+++ b/README.md
@@ -45,6 +45,7 @@ def alert_cbck(alert_code, alert_msg):
     if not alert_msg:
         alert_msg = 'no msg'
     print(f'{alert_msg} (code {alert_code})')
+
 c = CDCStream(
     alert_callback=alert_cbck,
     summary_extractor=dilca_workflow,
diff --git a/cdcstream/cdcstream.py b/cdcstream/cdcstream.py
index 60d5141..c8a2362 100644
--- a/cdcstream/cdcstream.py
+++ b/cdcstream/cdcstream.py
@@ -44,7 +44,7 @@ class UnsupervisedDriftDetector(DriftDetector):
 class CDCStream(UnsupervisedDriftDetector):
 
     def __init__(self,
-                 alert_callback: Callable,
+                 alert_callback: Callable=None,
                  summary_extractor: Callable=dilca_workflow,
                  summary_extractor_args: dict={'nominal_cols': 'all'},
                  factor_warn: float=2.0,
@@ -66,9 +66,9 @@ def __init__(self,
         }
 
         Args:
-            alert_callback (Callable): Function being called after each batch with an alert code of
-                ALERT_NONE, ALERT_WARN, ALERT_CHANGE. Must accept as arguments: alert_code: int,
-                alert_msg: str.
+            alert_callback (Callable, optional): Function being called after each batch with an
+                alert code of ALERT_NONE, ALERT_WARN, ALERT_CHANGE. Must accept as arguments:
+                alert_code: int, alert_msg: str. Defaults to None.
             summary_extractor (Callable, optional): Function for extracting a summary value from a
                 batch of data. Must accept as first parameter: data; as named parameter:
                 supervised. Defaults to cdcstream.dilca_wrapper.dilca_workflow.
@@ -134,6 +134,7 @@ def feed_new_batch(self, batch: pd.DataFrame) -> None:
     def _cycle_routine(self) -> None:
         """Main cycle of drift detector. It is being called with each new batch being fed.
         """
+        self._reset()
         self._extract_current_batch_summary_statistic()
         self._std_extrema_forgetting()  # BEFORE history statistics (especially stds) are being computed
         self._compute_history_statistics()
@@ -152,8 +153,6 @@ def _cleanup_current_cycle(self) -> None:
         if self.current_change:  # React to CHANGE
             self.reset_history()
             self.start_cooldown()
-        self.current_warn = False
-        self.current_change = False
 
         if self.batch_current_summary_statistic is not None:
             self.history.append(self.batch_current_summary_statistic)
@@ -224,6 +223,10 @@ def start_cooldown(self) -> None:
         """
         self._cur_cooldown_cycles = self.cooldown_cycles
 
+    def _reset(self):
+        self.current_warn = False
+        self.current_change = False
+
     def reset_history(self) -> None:
         self.history = []
 
@@ -262,7 +265,10 @@ def _alert(self) -> None:
         else:
             alert_code = self.ALERT_NONE
             alert_msg = self.ALERT_NONE_MSG
-        self._alert_callback(alert_code, alert_msg)
+        try:
+            self._alert_callback(alert_code, alert_msg)
+        except TypeError:
+            pass  # if user provided no alert_callback
 
     def _update_log(self) -> None:
         log_el = ()
@@ -317,6 +323,7 @@ def alert_cbck(alert_code, alert_msg):
         if not alert_msg:
             alert_msg = 'no msg'
         print(f'{alert_msg} (code {alert_code})')
+
     c = CDCStream(
         alert_callback=alert_cbck,
         summary_extractor=dilca_workflow,