diff --git a/neo/rawio/blackrockrawio.py b/neo/rawio/blackrockrawio.py
index c6d946fa8..1ef78a666 100644
--- a/neo/rawio/blackrockrawio.py
+++ b/neo/rawio/blackrockrawio.py
@@ -986,7 +986,8 @@ def __read_nsx_dataheader_variant_c(
         index = 0
 
         if offset is None:
-            offset = self.__nsx_basic_header[nsx_nb]["bytes_in_headers"]
+            # This is read as an uint32 numpy scalar from the header so we transform it to python int
+            offset = int(self.__nsx_basic_header[nsx_nb]["bytes_in_headers"])
 
         ptp_dt = [
             ("reserved", "uint8"),