diff --git a/scripts/wk/hw/benchmark.py b/scripts/wk/hw/benchmark.py
index 3b6481e3..8aebf51d 100644
--- a/scripts/wk/hw/benchmark.py
+++ b/scripts/wk/hw/benchmark.py
@@ -66,6 +66,8 @@ def calc_io_dd_values(dev_size, test_mode=False) -> dict[str, int]:
 
   test_mode limits the benchmark to IO_MINIMUM_TEST_SIZE (if possible)
   """
+  if test_mode and dev_size > IO_MINIMUM_TEST_SIZE:
+    dev_size = IO_MINIMUM_TEST_SIZE
   read_total = min(IO_MINIMUM_TEST_SIZE, dev_size)
   read_total = max(read_total, dev_size*IO_ALT_TEST_SIZE_FACTOR)
   read_chunks = int(read_total // IO_CHUNK_SIZE)