diff --git a/tests/test_io.py b/tests/test_io.py
index 0f49776..66f5aaa 100644
--- a/tests/test_io.py
+++ b/tests/test_io.py
@@ -6,7 +6,6 @@
 from pyhepmc._core import stringstream, pyiostream
 from io import BytesIO
 from pathlib import Path
-import numpy as np
 import typing
 import gzip
 from sys import version_info