diff --git a/lightningd/lightningd.c b/lightningd/lightningd.c
index c7cbedd2b..dc20c3428 100644
--- a/lightningd/lightningd.c
+++ b/lightningd/lightningd.c
@@ -733,6 +733,7 @@ static struct feature_set *default_features(const tal_t *ctx)
 		OPTIONAL_FEATURE(OPT_GOSSIP_QUERIES_EX),
 		OPTIONAL_FEATURE(OPT_STATIC_REMOTEKEY),
 #if EXPERIMENTAL_FEATURES
+		OPTIONAL_FEATURE(OPT_ANCHOR_OUTPUTS),
 		OPTIONAL_FEATURE(OPT_ONION_MESSAGES),
 #endif
 	};
diff --git a/tests/test_connection.py b/tests/test_connection.py
index bc97748d4..ec93cc3a3 100644
--- a/tests/test_connection.py
+++ b/tests/test_connection.py
@@ -8,7 +8,8 @@ from utils import (
     DEVELOPER, only_one, wait_for, sync_blockheight, TIMEOUT,
     expected_peer_features, expected_node_features,
     expected_channel_features,
-    check_coin_moves, first_channel_id, account_balance, basic_fee
+    check_coin_moves, first_channel_id, account_balance, basic_fee,
+    EXPERIMENTAL_FEATURES
 )
 from bitcoin.core import CMutableTransaction, CMutableTxOut
 
@@ -138,6 +139,7 @@ def test_bad_opening(node_factory):
     l2.daemon.wait_for_log('to_self_delay 100 larger than 99')
 
 
+@unittest.skipIf(EXPERIMENTAL_FEATURES, "FIXME: anchor_outputs changes numbers")
 @unittest.skipIf(not DEVELOPER, "gossip without DEVELOPER=1 is slow")
 @unittest.skipIf(TEST_NETWORK != 'regtest', "Fee computation and limits are network specific")
 @pytest.mark.slow_test
@@ -2176,8 +2178,9 @@ def test_feerate_spam(node_factory, chainparams):
     # Now change feerates to something l1 can't afford.
     l1.set_feerates((100000, 100000, 100000, 100000))
 
-    # It will raise as far as it can (48000)
-    l1.daemon.wait_for_log('Setting REMOTE feerate to 48000')
+    # It will raise as far as it can (48000) (30000 for option_anchor_outputs)
+    maxfeerate = 30000 if EXPERIMENTAL_FEATURES else 48000
+    l1.daemon.wait_for_log('Setting REMOTE feerate to {}'.format(maxfeerate))
     l1.daemon.wait_for_log('peer_out WIRE_UPDATE_FEE')
 
     # But it won't do it again once it's at max.
diff --git a/tests/test_misc.py b/tests/test_misc.py
index b41c2b662..9e3cfd0ef 100644
--- a/tests/test_misc.py
+++ b/tests/test_misc.py
@@ -1537,8 +1537,13 @@ def test_feerates(node_factory):
     htlc_feerate = feerates["perkw"]["htlc_resolution"]
     htlc_timeout_cost = feerates["onchain_fee_estimates"]["htlc_timeout_satoshis"]
     htlc_success_cost = feerates["onchain_fee_estimates"]["htlc_success_satoshis"]
-    assert htlc_timeout_cost == htlc_feerate * 663 // 1000
-    assert htlc_success_cost == htlc_feerate * 703 // 1000
+    if EXPERIMENTAL_FEATURES:
+        # option_anchor_outputs
+        assert htlc_timeout_cost == htlc_feerate * 666 // 1000
+        assert htlc_success_cost == htlc_feerate * 706 // 1000
+    else:
+        assert htlc_timeout_cost == htlc_feerate * 663 // 1000
+        assert htlc_success_cost == htlc_feerate * 703 // 1000
 
 
 def test_logging(node_factory):
@@ -1887,6 +1892,7 @@ def test_list_features_only(node_factory):
                 'option_basic_mpp/odd',
                 ]
     if EXPERIMENTAL_FEATURES:
+        expected += ['option_anchor_outputs/odd']
         expected += ['option_unknown_102/odd']
     assert features == expected
 
diff --git a/tests/test_pay.py b/tests/test_pay.py
index 6c3f7eb0a..dddabdb05 100644
--- a/tests/test_pay.py
+++ b/tests/test_pay.py
@@ -627,11 +627,30 @@ def test_sendpay_cant_afford(node_factory):
     with pytest.raises(RpcError):
         l1.pay(l2, 10**9 + 1)
 
-    # This is the fee, which needs to be taken into account for l1.
-    available = 10**9 - 32040000
     # Reserve is 1%.
     reserve = 10**7
 
+    # # This is how we recalc constants (v. v. slow!)
+    # minimum = 1
+    # maximum = 10**9
+    # while maximum - minimum > 1:
+    #     l1, l2 = node_factory.line_graph(2, fundamount=10**6,
+    #                                      opts={'feerates': (15000, 15000, 15000, 15000)})
+    #     try:
+    #         l1.pay(l2, (minimum + maximum) // 2)
+    #         minimum = (minimum + maximum) // 2
+    #     except RpcError:
+    #         maximum = (minimum + maximum) // 2
+    #     print("{} - {}".format(minimum, maximum))
+    # assert False
+
+    # This is the fee, which needs to be taken into account for l1.
+    if EXPERIMENTAL_FEATURES:
+        # option_anchor_outputs
+        available = 10**9 - 44700000
+    else:
+        available = 10**9 - 32040000
+
     # Can't pay past reserve.
     with pytest.raises(RpcError):
         l1.pay(l2, available)
diff --git a/tests/test_plugin.py b/tests/test_plugin.py
index c5952ca6f..d52e6340d 100644
--- a/tests/test_plugin.py
+++ b/tests/test_plugin.py
@@ -8,7 +8,7 @@ from utils import (
     DEVELOPER, only_one, sync_blockheight, TIMEOUT, wait_for, TEST_NETWORK,
     DEPRECATED_APIS, expected_peer_features, expected_node_features,
     expected_channel_features, account_balance,
-    check_coin_moves, first_channel_id, check_coin_moves_idx
+    check_coin_moves, first_channel_id, check_coin_moves_idx, EXPERIMENTAL_FEATURES
 )
 from pyln.testing.utils import TailableProc
 
@@ -1438,6 +1438,26 @@ def test_coin_movement_notices(node_factory, bitcoind, chainparams):
             {'type': 'chain_mvt', 'credit': 100001000, 'debit': 0, 'tag': 'deposit'},
             {'type': 'chain_mvt', 'credit': 941045000, 'debit': 0, 'tag': 'deposit'},
         ]
+    elif EXPERIMENTAL_FEATURES:
+        # option_anchor_outputs
+        l2_l3_mvts = [
+            {'type': 'chain_mvt', 'credit': 1000000000, 'debit': 0, 'tag': 'deposit'},
+            {'type': 'channel_mvt', 'credit': 0, 'debit': 100000000, 'tag': 'routed'},
+            {'type': 'channel_mvt', 'credit': 50000501, 'debit': 0, 'tag': 'routed'},
+            {'type': 'chain_mvt', 'credit': 0, 'debit': 8430501, 'tag': 'chain_fees'},
+            {'type': 'chain_mvt', 'credit': 0, 'debit': 941570000, 'tag': 'withdrawal'},
+        ]
+
+        l2_wallet_mvts = [
+            {'type': 'chain_mvt', 'credit': 2000000000, 'debit': 0, 'tag': 'deposit'},
+            {'type': 'chain_mvt', 'credit': 0, 'debit': 0, 'tag': 'spend_track'},
+            {'type': 'chain_mvt', 'credit': 0, 'debit': 995425000, 'tag': 'withdrawal'},
+            {'type': 'chain_mvt', 'credit': 0, 'debit': 1000000000, 'tag': 'withdrawal'},
+            {'type': 'chain_mvt', 'credit': 0, 'debit': 4575000, 'tag': 'chain_fees'},
+            {'type': 'chain_mvt', 'credit': 995425000, 'debit': 0, 'tag': 'deposit'},
+            {'type': 'chain_mvt', 'credit': 100001000, 'debit': 0, 'tag': 'deposit'},
+            {'type': 'chain_mvt', 'credit': 941570000, 'debit': 0, 'tag': 'deposit'},
+        ]
     else:
         l2_l3_mvts = [
             {'type': 'chain_mvt', 'credit': 1000000000, 'debit': 0, 'tag': 'deposit'},
diff --git a/tests/utils.py b/tests/utils.py
index ffb1e355b..565cdd8bc 100644
--- a/tests/utils.py
+++ b/tests/utils.py
@@ -23,6 +23,8 @@ def expected_peer_features(wumbo_channels=False, extra=[]):
     if EXPERIMENTAL_FEATURES:
         # OPT_ONION_MESSAGES
         features += [103]
+        # option_anchor_outputs
+        features += [21]
     if wumbo_channels:
         features += [19]
     return hex_bits(features + extra)
@@ -36,6 +38,8 @@ def expected_node_features(wumbo_channels=False, extra=[]):
     if EXPERIMENTAL_FEATURES:
         # OPT_ONION_MESSAGES
         features += [103]
+        # option_anchor_outputs
+        features += [21]
     if wumbo_channels:
         features += [19]
     return hex_bits(features + extra)
@@ -105,7 +109,7 @@ def first_channel_id(n1, n2):
 
 
 def basic_fee(feerate):
-    if False:  # FIXME-anchor
+    if EXPERIMENTAL_FEATURES:
         # option_anchor_outputs
         weight = 1124
     else: