diff --git a/doc/release-notes.md b/doc/release-notes.md
--- a/doc/release-notes.md
+++ b/doc/release-notes.md
@@ -14,3 +14,6 @@
  - The `savemempool` RPC now returns the path to the saved mempool in the `filename` field.
  - Bitcoin ABC now supports User-space, Statically Defined Tracing (USDT).
    For now only a few tracepoints are available, see [tracing.md](/doc/tracing.md) for more info.
+ - Avalanche is now enabled by default. It is still possible to disable it by
+   using `-avalanche=0` on the command line, or setting `avalanche=0` in the
+   `bitcoin.conf` file.
diff --git a/src/avalanche/avalanche.h b/src/avalanche/avalanche.h
--- a/src/avalanche/avalanche.h
+++ b/src/avalanche/avalanche.h
@@ -19,7 +19,7 @@
 /**
  * Is avalanche enabled by default.
  */
-static constexpr bool AVALANCHE_DEFAULT_ENABLED = false;
+static constexpr bool AVALANCHE_DEFAULT_ENABLED = true;
 
 /**
  * Conflicting proofs cooldown time default value in seconds.
diff --git a/test/functional/abc-invalid-chains.py b/test/functional/abc-invalid-chains.py
--- a/test/functional/abc-invalid-chains.py
+++ b/test/functional/abc-invalid-chains.py
@@ -18,7 +18,10 @@
         self.tip = None
         self.blocks = {}
         self.block_heights = {}
-        self.extra_args = [["-whitelist=noban@127.0.0.1"]]
+        self.extra_args = [[
+            "-whitelist=noban@127.0.0.1",
+            "-automaticunparking=1",
+        ]]
 
     def next_block(self, number):
         if self.tip is None:
diff --git a/test/functional/abc-mempool-coherence-on-activations.py b/test/functional/abc-mempool-coherence-on-activations.py
--- a/test/functional/abc-mempool-coherence-on-activations.py
+++ b/test/functional/abc-mempool-coherence-on-activations.py
@@ -129,9 +129,12 @@
         self.block_heights = {}
         self.tip = None
         self.blocks = {}
-        self.extra_args = [['-whitelist=noban@127.0.0.1',
-                            EXTRA_ARG,
-                            '-acceptnonstdtxn=1']]
+        self.extra_args = [[
+            '-whitelist=noban@127.0.0.1',
+            EXTRA_ARG,
+            '-acceptnonstdtxn=1',
+            '-automaticunparking=1',
+        ]]
 
     def next_block(self, number):
         if self.tip is None:
diff --git a/test/functional/abc-parkedchain.py b/test/functional/abc-parkedchain.py
--- a/test/functional/abc-parkedchain.py
+++ b/test/functional/abc-parkedchain.py
@@ -2,7 +2,7 @@
 # Copyright (c) 2018 The Bitcoin developers
 # Distributed under the MIT software license, see the accompanying
 # file COPYING or http://www.opensource.org/licenses/mit-license.php.
-"""Test the parckblock and unparkblock RPC calls."""
+"""Test the parkblock and unparkblock RPC calls."""
 
 from test_framework.test_framework import BitcoinTestFramework
 from test_framework.util import assert_equal
@@ -11,8 +11,17 @@
 class ParkedChainTest(BitcoinTestFramework):
     def set_test_params(self):
         self.num_nodes = 2
-        self.extra_args = [["-noparkdeepreorg",
-                            "-noautomaticunparking", "-whitelist=noban@127.0.0.1"], ["-maxreorgdepth=-1"]]
+        self.extra_args = [
+            [
+                "-noparkdeepreorg",
+                "-noautomaticunparking",
+                "-whitelist=noban@127.0.0.1",
+            ],
+            [
+                "-automaticunparking=1",
+                "-maxreorgdepth=-1"
+            ]
+        ]
 
     def skip_test_if_missing_module(self):
         self.skip_if_no_wallet()
@@ -216,7 +225,7 @@
                                )
         wait_for_parked_block(node.getbestblockhash())
         # Restart the parking node without parkdeepreorg.
-        self.restart_node(1, ["-parkdeepreorg=0"])
+        self.restart_node(1, self.extra_args[1] + ["-parkdeepreorg=0"])
         parking_node = self.nodes[1]
         self.connect_nodes(node.index, parking_node.index)
         # The other chain should still be marked 'parked'.
diff --git a/test/functional/feature_bip68_sequence.py b/test/functional/feature_bip68_sequence.py
--- a/test/functional/feature_bip68_sequence.py
+++ b/test/functional/feature_bip68_sequence.py
@@ -48,7 +48,8 @@
             ],
             [
                 "-acceptnonstdtxn=0",
-                "-maxreorgdepth=-1"
+                "-maxreorgdepth=-1",
+                "-automaticunparking=1",
             ]
         ]
 
diff --git a/test/functional/feature_coinstatsindex.py b/test/functional/feature_coinstatsindex.py
--- a/test/functional/feature_coinstatsindex.py
+++ b/test/functional/feature_coinstatsindex.py
@@ -31,8 +31,12 @@
         self.num_nodes = 2
         self.supports_cli = False
         self.extra_args = [
-            [],
-            ["-coinstatsindex"]
+            [
+                "-automaticunparking=1",
+            ],
+            [
+                "-coinstatsindex",
+            ]
         ]
 
     def skip_test_if_missing_module(self):
diff --git a/test/functional/p2p_fingerprint.py b/test/functional/p2p_fingerprint.py
--- a/test/functional/p2p_fingerprint.py
+++ b/test/functional/p2p_fingerprint.py
@@ -83,6 +83,7 @@
             node0.send_and_ping(msg_block(block))
 
         # Check that reorg succeeded
+        self.nodes[0].unparkblock(new_blocks[-1].hash)
         assert_equal(self.nodes[0].getblockcount(), 13)
 
         stale_hash = int(block_hashes[-1], 16)