diff --git a/tiledb/array.py b/tiledb/array.py
index 986c693e09..22d1fbd91b 100644
--- a/tiledb/array.py
+++ b/tiledb/array.py
@@ -899,7 +899,7 @@ def _write_array(
             q.set_data_buffer(
                 buffer_name,
                 output_values[i],
-                buffer_sizes[i] * ncells,
+                np.uint64(buffer_sizes[i] * ncells),
             )
 
             # Set offsets buffer