diff --git a/neo/rawio/plexonrawio.py b/neo/rawio/plexonrawio.py
index 5593ab2e9..cc79417e3 100644
--- a/neo/rawio/plexonrawio.py
+++ b/neo/rawio/plexonrawio.py
@@ -209,7 +209,9 @@ def _parse_header(self):
                 for index, pos in enumerate(positions):
                     bl_header = data[pos : pos + 16].view(DataBlockHeader)[0]
 
-                    timestamp = bl_header["UpperByteOf5ByteTimestamp"] * 2**32 + bl_header["TimeStamp"]
+                    current_upper_byte_of_5_byte_timestamp = int(bl_header["UpperByteOf5ByteTimestamp"])
+                    current_bl_timestamp = int(bl_header["TimeStamp"])
+                    timestamp = current_upper_byte_of_5_byte_timestamp * 2**32 + current_bl_timestamp
                     n1 = bl_header["NumberOfWaveforms"]
                     n2 = bl_header["NumberOfWordsInWaveform"]
                     sample_count = n1 * n2
diff --git a/pyproject.toml b/pyproject.toml
index c6fd2fa19..79cc1a849 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -80,7 +80,8 @@ docs = [
     "matplotlib",
     "nixio",
     "pynwb",
-    "igor2"
+    "igor2",
+    "numpy<2.0" # https://github.com/NeuralEnsemble/python-neo/pull/1612
 ]
 
 dev = [