--- a/buggy.py
+++ b/buggy.py
@@ -1,9 +1,9 @@
-from dataclasses import dataclass
+from dataclasses import dataclass, field
 
 
 @dataclass
 class Metrics:
-    counters: dict[str, int] = {}
+    counters: dict[str, int] = field(default_factory=dict)
 
 
 def bump(metrics: Metrics, name: str) -> int:
