diff --git a/src/cli.py b/src/cli.py
index a26788d..c0614b1 100644
--- a/src/cli.py
+++ b/src/cli.py
@@ -19,6 +19,7 @@ def _comma_seperated_argument(_ctx, _param, value):
         return value.split(",")
     return []
 
+
 # Accepts value string in format "key=val". Returns dict {key: val}.
 # * If value is None - returns empty dict
 def _eq_sign_separated_argument_to_dict(_ctx, _param, value):
@@ -30,6 +31,7 @@ def _eq_sign_separated_argument_to_dict(_ctx, _param, value):
         return dict_of_key_value_pairs
     return {}
 
+
 @click.command(help=cmd_help)
 @click.option(
     "--broker-url",
@@ -159,5 +161,5 @@ def cli(  # pylint: disable=too-many-arguments,too-many-positional-arguments,too
         generic_hostname_task_sent_metric,
         queues,
         metric_prefix,
-        static_label
+        static_label,
     ).run(ctx.params)
diff --git a/src/exporter.py b/src/exporter.py
index 7ca073a..609227a 100644
--- a/src/exporter.py
+++ b/src/exporter.py
@@ -29,7 +29,7 @@ def __init__(
         generic_hostname_task_sent_metric=False,
         initial_queues=None,
         metric_prefix="celery_",
-        static_label=[]
+        static_label=None,
     ):
         self.registry = CollectorRegistry(auto_describe=True)
         self.queue_cache = set(initial_queues or [])
@@ -39,10 +39,10 @@ def __init__(
             purge_offline_worker_metrics_seconds
         )
         self.generic_hostname_task_sent_metric = generic_hostname_task_sent_metric
-        
+
         # Static labels
-        self.static_label = static_label
-        self.static_label_keys = static_label.keys()
+        self.static_label = static_label or {}
+        self.static_label_keys = self.static_label.keys()
 
         self.state_counters = {
             "task-sent": Counter(
@@ -72,7 +72,13 @@ def __init__(
             "task-failed": Counter(
                 f"{metric_prefix}task_failed",
                 "Sent if the execution of the task failed.",
-                ["name", "hostname", "exception", "queue_name", *self.static_label_keys],
+                [
+                    "name",
+                    "hostname",
+                    "exception",
+                    "queue_name",
+                    *self.static_label_keys,
+                ],
                 registry=self.registry,
             ),
             "task-rejected": Counter(
@@ -150,7 +156,9 @@ def scrape(self):
     def forget_worker(self, hostname):
         if hostname in self.worker_last_seen:
             self.celery_worker_up.labels(hostname=hostname, **self.static_label).set(0)
-            self.worker_tasks_active.labels(hostname=hostname, **self.static_label).set(0)
+            self.worker_tasks_active.labels(hostname=hostname, **self.static_label).set(
+                0
+            )
             logger.debug(
                 "Updated gauge='{}' value='{}'", self.worker_tasks_active._name, 0
             )
@@ -244,19 +252,21 @@ def track_queue_metrics(self):
             for queue in self.queue_cache:
                 if transport in ["amqp", "amqps", "memory"]:
                     consumer_count = rabbitmq_queue_consumer_count(connection, queue)
-                    self.celery_active_consumer_count.labels(queue_name=queue, **self.static_label).set(
-                        consumer_count
-                    )
-
-                self.celery_active_process_count.labels(queue_name=queue, **self.static_label).set(
-                    processes_per_queue[queue]
-                )
-                self.celery_active_worker_count.labels(queue_name=queue, **self.static_label).set(
-                    workers_per_queue[queue]
-                )
+                    self.celery_active_consumer_count.labels(
+                        queue_name=queue, **self.static_label
+                    ).set(consumer_count)
+
+                self.celery_active_process_count.labels(
+                    queue_name=queue, **self.static_label
+                ).set(processes_per_queue[queue])
+                self.celery_active_worker_count.labels(
+                    queue_name=queue, **self.static_label
+                ).set(workers_per_queue[queue])
                 length = queue_length(transport, connection, queue)
                 if length is not None:
-                    self.celery_queue_length.labels(queue_name=queue, **self.static_label).set(length)
+                    self.celery_queue_length.labels(
+                        queue_name=queue, **self.static_label
+                    ).set(length)
 
     def track_task_event(self, event):
         self.state.event(event)
@@ -270,7 +280,7 @@ def track_task_event(self, event):
             "name": task.name,
             "hostname": get_hostname(task.hostname),
             "queue_name": getattr(task, "queue", "celery"),
-            **self.static_label
+            **self.static_label,
         }
         if event["type"] == "task-sent" and self.generic_hostname_task_sent_metric:
             labels["hostname"] = "generic"
@@ -334,7 +344,9 @@ def track_worker_heartbeat(self, event):
         active = worker_state.active or 0
         up = 1 if worker_state.alive else 0
         self.celery_worker_up.labels(hostname=hostname, **self.static_label).set(up)
-        self.worker_tasks_active.labels(hostname=hostname, **self.static_label).set(active)
+        self.worker_tasks_active.labels(hostname=hostname, **self.static_label).set(
+            active
+        )
         logger.debug(
             "Updated gauge='{}' value='{}'", self.worker_tasks_active._name, active
         )