diff --git a/test/functional/abc-p2p-compactblocks.py b/test/functional/abc-p2p-compactblocks.py
--- a/test/functional/abc-p2p-compactblocks.py
+++ b/test/functional/abc-p2p-compactblocks.py
@@ -19,6 +19,7 @@
 from test_framework.script import *
 from test_framework.cdefs import (ONE_MEGABYTE, LEGACY_MAX_BLOCK_SIZE,
                                   MAX_BLOCK_SIGOPS_PER_MB, MAX_TX_SIGOPS_COUNT)
+from test_framework.txtools import pad_tx
 from collections import deque
 
 
@@ -97,8 +98,12 @@
         self.test.run()
 
     def add_transactions_to_block(self, block, tx_list):
-        [tx.rehash() for tx in tx_list]
-        block.vtx.extend(tx_list)
+        for tx in tx_list:
+            pad_tx(tx)
+            tx.rehash()
+        tx_list = block.vtx[1:] + tx_list
+        block.vtx = [block.vtx[0]] + \
+            sorted(tx_list, key=lambda tx: tx.get_id())
 
     # this is a little handier to use than the version in blocktools.py
     def create_tx(self, spend_tx, n, value, script=CScript([OP_TRUE])):
@@ -193,6 +198,10 @@
                 self.add_transactions_to_block(block, [tx])
                 current_block_size += len(tx.serialize())
 
+            # Order transactions canonically
+            block.vtx = [block.vtx[0]] + \
+                sorted(block.vtx[1:], key=lambda tx: tx.get_id())
+
             # Now that we added a bunch of transaction, we need to recompute
             # the merkle root.
             block.hashMerkleRoot = block.calc_merkle_root()