diff --git a/tests/extmod/uctypes_array_assign_le.py b/tests/extmod/uctypes_array_assign_le.py
index d822faf7e8a9..b7fcdfb49c05 100644
--- a/tests/extmod/uctypes_array_assign_le.py
+++ b/tests/extmod/uctypes_array_assign_le.py
@@ -18,7 +18,7 @@
     "arr8": (uctypes.ARRAY | 1, 1, {"l": uctypes.UINT32 | 0}),
 }
 
-data = bytearray(5)
+data = bytearray(6)
 
 S = uctypes.struct(uctypes.addressof(data), desc, uctypes.LITTLE_ENDIAN)