diff --git a/km3io/rootio.py b/km3io/rootio.py
index 34f0b68d3740a4034e69197f8b170a2c1d8400cb..60eecb8734cb5e26349dd3b698a9cc2569b3d2cf 100644
--- a/km3io/rootio.py
+++ b/km3io/rootio.py
@@ -158,6 +158,9 @@ class Branch:
         if isinstance(item, str):
             return self.__getkey__(item)
 
+        if isinstance(item, (np.int32, np.int64)):
+            item = int(item)
+
         # if item.__class__.__name__ == "ChunkedArray":
         #     item = np.array(item)