diff --git a/pyproject.toml b/pyproject.toml
index f804d07..708865d 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -1,6 +1,6 @@
 [tool.poetry]
 name = "tibert"
-version = "0.3.0"
+version = "0.3.1"
 description = "BERT for Coreference Resolution"
 authors = ["Arthur Amalvy <arthur.amalvy@univ-avignon.fr>"]
 license = "GPL-3.0-only"
diff --git a/tibert/score.py b/tibert/score.py
index 510353a..4c47846 100644
--- a/tibert/score.py
+++ b/tibert/score.py
@@ -115,7 +115,7 @@ def score_muc(
     np.int = int  # type: ignore
     np.bool = bool  # type: ignore
 
-    precisions, recalls, f1s = []
+    precisions, recalls, f1s = [], [], []
     for pred, ref in zip(preds, refs):
         p, r, f1 = _neleval_precision_recall_f1(pred, ref, muc)
         precisions.append(p)