diff --git a/test/functional/test_framework/test_node.py b/test/functional/test_framework/test_node.py
index 4ac7db2030e..60ca9269a5b 100755
--- a/test/functional/test_framework/test_node.py
+++ b/test/functional/test_framework/test_node.py
@@ -46,6 +46,8 @@ BITCOIND_PROC_WAIT_TIMEOUT = 60
 # The size of the blocks xor key
 # from InitBlocksdirXorKey::xor_key.size()
 NUM_XOR_BYTES = 8
+# The null blocks key (all 0s)
+NULL_BLK_XOR_KEY = bytes([0] * NUM_XOR_BYTES)
 
 
 class FailedToStartError(Exception):