diff --git a/lightningd/anchorspend.c b/lightningd/anchorspend.c
index dccd98268..aa64c4316 100644
--- a/lightningd/anchorspend.c
+++ b/lightningd/anchorspend.c
@@ -219,7 +219,7 @@ struct anchor_details *create_anchor_details(const tal_t *ctx,
 		final_deadline = adet->vals[tal_count(adet->vals) - 1].block;
 
 	/* "Two weeks later" */
-	v.block = final_deadline + 2016;
+	v.block = final_deadline + ld->dev_low_prio_anchor_blocks;
 	v.msat = AMOUNT_MSAT(0);
 	v.important = false;
 	tal_arr_expand(&adet->vals, v);
diff --git a/lightningd/lightningd.c b/lightningd/lightningd.c
index c8b1eda2a..aa6ab1824 100644
--- a/lightningd/lightningd.c
+++ b/lightningd/lightningd.c
@@ -143,6 +143,7 @@ static struct lightningd *new_lightningd(const tal_t *ctx)
 	ld->dev_no_htlc_timeout = false;
 	ld->dev_no_version_checks = false;
 	ld->dev_max_funding_unconfirmed = 2016;
+	ld->dev_low_prio_anchor_blocks = 2016;
 	ld->dev_ignore_modern_onion = false;
 	ld->dev_disable_commit = -1;
 	ld->dev_no_ping_timer = false;
diff --git a/lightningd/lightningd.h b/lightningd/lightningd.h
index 37ae7b930..6834aa38a 100644
--- a/lightningd/lightningd.h
+++ b/lightningd/lightningd.h
@@ -307,6 +307,9 @@ struct lightningd {
 	bool dev_throttle_gossip;
 	bool dev_suppress_gossip;
 
+	/* How long to aim for low-priority commitment closes */
+	u32 dev_low_prio_anchor_blocks;
+
 	/* Speedup reconnect delay, for testing. */
 	bool dev_fast_reconnect;
 
diff --git a/lightningd/options.c b/lightningd/options.c
index 65c2986e8..a2c0f46af 100644
--- a/lightningd/options.c
+++ b/lightningd/options.c
@@ -969,15 +969,19 @@ static void dev_register_opts(struct lightningd *ld)
 		     opt_set_bool,
 		     &ld->dev_limit_connections_inflight,
 		     "Throttle connection limiting down for testing.");
+	clnopt_witharg("--autoconnect-seeker-peers", OPT_SHOWINT,
+		       opt_set_u32, opt_show_u32,
+		       &ld->autoconnect_seeker_peers,
+		       "Seeker autoconnects to maintain this minimum number of gossip peers");
+	clnopt_witharg("--dev-low-prio-anchor-blocks", OPT_DEV|OPT_SHOWINT,
+		       opt_set_u32, opt_show_u32,
+		       &ld->dev_low_prio_anchor_blocks,
+		       "How many blocks to aim for low-priority anchor closes (default: 2016)");
 	/* This is handled directly in daemon_developer_mode(), so we ignore it here */
 	clnopt_noarg("--dev-debug-self", OPT_DEV,
 		     opt_ignore,
 		     NULL,
 		     "Fire up a terminal window with a debugger in it on initialization");
-	clnopt_witharg("--autoconnect-seeker-peers", OPT_SHOWINT,
-		       opt_set_u32, opt_show_u32,
-		       &ld->autoconnect_seeker_peers,
-		       "Seeker autoconnects to maintain this minimum number of gossip peers");
 }
 
 static const struct config testnet_config = {
diff --git a/tests/test_closing.py b/tests/test_closing.py
index 90883c840..047d9e420 100644
--- a/tests/test_closing.py
+++ b/tests/test_closing.py
@@ -4219,3 +4219,32 @@ def test_onchain_slow_anchor(node_factory, bitcoind):
 
     # We will have a super-low-prio anchor spend.
     l1.daemon.wait_for_log(r"Low-priority anchorspend aiming for block {} \(feerate 253\)".format(close_start_depth + 2016))
+
+    # Restart with reduced block time.
+    l1.stop()
+    l1.daemon.opts['dev-low-prio-anchor-blocks'] = 20
+    l1.start()
+
+    l1.daemon.wait_for_log("Low-priority anchorspend aiming for block {}".format(close_start_depth + 20))
+    l1.daemon.wait_for_log("Anchorspend for local commit tx")
+
+    # Won't go under 12 blocks though.
+
+    # Make sure it sees all these blocks at once, to avoid test flakes!
+    l1.stop()
+    bitcoind.generate_block(7)
+    l1.start()
+
+    height = bitcoind.rpc.getblockchaininfo()['blocks']
+    l1.daemon.wait_for_log(r"Low-priority anchorspend aiming for block {} \(feerate 7458\)".format(height + 13))
+    l1.daemon.wait_for_log(r"Anchorspend for local commit tx fee 12335sat \(w=714\), commit_tx fee 4545sat \(w=768\): package feerate 11390 perkw")
+    assert not l1.daemon.is_in_log("Low-priority anchorspend aiming for block {}".format(height + 12))
+
+    bitcoind.generate_block(1)
+    height = bitcoind.rpc.getblockchaininfo()['blocks']
+    l1.daemon.wait_for_log(r"Low-priority anchorspend aiming for block {} \(feerate 7500\)".format(height + 12))
+    # Note: fee is too similar, so won't try to RBF, so no "Anchorspend for local commit tx"
+
+    bitcoind.generate_block(1)
+    height = bitcoind.rpc.getblockchaininfo()['blocks']
+    l1.daemon.wait_for_log(r"Low-priority anchorspend aiming for block {} \(feerate 7500\)".format(height + 12))