diff --git a/event_count_logger.py b/event_count_logger.py
index 9dd9814..ec85396 100644
--- a/event_count_logger.py
+++ b/event_count_logger.py
@@ -223,11 +223,15 @@ def declare_event_id(self, event_id: str):
         Create counter for event_id if it doesn't exist yet.
         Should be equivalent to listing the event ID in configuration file.
         """
-        if event_id not in self.event_ids:
-            self.event_ids.add(event_id)
-            if self.use_local_counters:
-                for int_counters in self.counters:
+        if self.use_local_counters:
+            with self.counter_lock:
+                if event_id in self.event_ids:
+                    return
+                for int_counters in self.counters.values():
                     int_counters[event_id] = 0
+                self.event_ids.add(event_id)
+        elif event_id not in self.event_ids:
+            self.event_ids.add(event_id)
 
     def declare_event_ids(self, event_ids: Iterable[str]):
         """
diff --git a/tests/test_event_count_logger.py b/tests/test_event_count_logger.py
new file mode 100644
index 0000000..ab3babd
--- /dev/null
+++ b/tests/test_event_count_logger.py
@@ -0,0 +1,48 @@
+import unittest
+from unittest.mock import Mock, call
+
+from event_count_logger import EventGroup
+
+
+class EventGroupTest(unittest.TestCase):
+    def test_auto_declares_event_with_local_counters(self):
+        redis = Mock()
+        group = EventGroup(
+            redis,
+            "dynamic",
+            [],
+            ["5m", "2h"],
+            auto_declare=True,
+            sync_limit=10,
+        )
+
+        group.log("new_event", count=2)
+
+        self.assertEqual(
+            {
+                "5m": {"new_event": 2},
+                "2h": {"new_event": 2},
+            },
+            group.counters,
+        )
+
+        group.sync()
+
+        self.assertEqual(
+            [
+                call("dynamic:5m:cur:new_event", amount=2),
+                call("dynamic:2h:cur:new_event", amount=2),
+            ],
+            redis.incr.call_args_list,
+        )
+        self.assertEqual(
+            {
+                "5m": {"new_event": 0},
+                "2h": {"new_event": 0},
+            },
+            group.counters,
+        )
+
+
+if __name__ == "__main__":
+    unittest.main()