test deltamode works

diff --git a/testing/conftest.py b/testing/conftest.py
index ccfd5c6..1916b22 100644
--- a/testing/conftest.py
+++ b/testing/conftest.py
@@ -2627,6 +2627,27 @@ def build_test_seed_vault():
         return sv
     return doit
 
+@pytest.fixture
+def get_deltamode(sim_exec):
+    # get current "deltamode" status: T or F
+    def doit():
+        return eval(sim_exec('RV.write(repr(pa.is_deltamode()))'))
+    return doit
+
+@pytest.fixture
+def set_deltamode(sim_exec):
+    # control current "deltamode" status: T or F
+    def doit(val):
+        # TC_DELTA_MODE   = const(0x0400)
+        if val:
+            sim_exec('pa.delay_required |= 0x400')
+        else:
+            sim_exec('pa.delay_required &= ~0x400')
+        
+    yield doit
+
+    doit(False)
+
 
 # useful fixtures
 from test_backup import backup_system
diff --git a/testing/test_hobble.py b/testing/test_hobble.py
index 3cba9fe..dc4ed9e 100644
--- a/testing/test_hobble.py
+++ b/testing/test_hobble.py
@@ -17,6 +17,7 @@ from test_ux import word_menu_entry
 #
 # - test_teleport.py::test_teleport_ms_sign
 #    - verifies: MS psbt KT should still work in hobbled mode
+#
 # - test_teleport.py::test_hobble_limited
 #    - verifies: scan a KT and have it rejected if not PSBT type: so R and E types
 
@@ -392,8 +393,6 @@ def test_h_usbcmds(en_okeys, set_hobble, dev):
             got = dev.send_recv(cmd)
         assert 'Spending policy in effect' in str(ee)
 
-# TODO: verify that PSBT can be "signed" when SP enabled and delta-mode pin is active. seed not wiped.
-
 
 # TODO verify whitelist of QR types is correct when in hobbled mode
 # - no private key material, no teleport starting, unless "okeys" is set
diff --git a/testing/test_se2.py b/testing/test_se2.py
index 75f1825..78d640a 100644
--- a/testing/test_se2.py
+++ b/testing/test_se2.py
@@ -916,6 +916,14 @@ def build_duress_wallets(request, seed_vault=False):
     return 4
 
 
+def test_deltamode_toggle(get_deltamode, set_deltamode):
+    # check test fixture works.
+    assert get_deltamode() == False
+    set_deltamode(True)
+    assert get_deltamode() == True
+    set_deltamode(False)
+    assert get_deltamode() == False
+
 
 # TODO
 # - make trick and do login, check arrives right state?
diff --git a/testing/test_sssp.py b/testing/test_sssp.py
index 264c207..b14d469 100644
--- a/testing/test_sssp.py
+++ b/testing/test_sssp.py
@@ -566,4 +566,56 @@ def test_use_trick_pin_as_unlock(hide, setup_sssp, cap_story, new_trick_pin, pic
     assert "already in use" in story
     assert "PIN codes must be unique" in story
 
+
+
+@pytest.mark.parametrize("active_policy", [False, True])
+def test_deltamode_signature(active_policy, setup_sssp, bitcoind, settings_set,
+                        start_sign, end_sign,
+                        set_deltamode, bitcoind_d_sim_watch, settings_get):
+
+    # verify that "deltamode" trick pins will work in SSSP mode
+    # - and that resulting signature is bad
+    # - device should **not** wipe itself
+
+    dest = "bcrt1qlk39jrclgnawa42tvhu2n7se987qm96qg8v76e"
+    wo = bitcoind_d_sim_watch
+    wo.keypoolrefill(20)
+
+    settings_set("chain", "XRT")
+
+    if active_policy:
+        setup_sssp("11-11", mag=100)
+
+    bitcoind.supply_wallet.sendtoaddress(address=wo.getnewaddress(), amount=2)
+    bitcoind.supply_wallet.generatetoaddress(1, bitcoind.supply_wallet.getnewaddress())
+
+    # create funded PSBT, first tx
+    # - within active policy.
+    init_block_height = bitcoind.supply_wallet.getblockchaininfo()["blocks"]  # block height
+    psbt_resp = wo.walletcreatefundedpsbt([], [{dest: 0.06}],
+                                          init_block_height, {"fee_rate":2, "replaceable": False})
+    psbt = psbt_resp.get("psbt")
+
+    po = BasicPSBT().parse(base64.b64decode(psbt))
+    assert po.parsed_txn.nLockTime == init_block_height
+
+    start_sign(base64.b64decode(psbt), finalize=True)
+    signed = end_sign(accept=True, finalize=True)
+
+    set_deltamode(True)
+
+    start_sign(base64.b64decode(psbt), finalize=True)
+    signed2 = end_sign(accept=True, finalize=True)
+
+    # check wrong signature happened
+    assert signed != signed2
+    probs = wo.testmempoolaccept([signed2.hex()])[0]
+    assert 'Signature must be zero' in probs['reject-reason'], probs
+    assert not probs['allowed']
+
+    # check right signature
+    no_probs = wo.testmempoolaccept([signed.hex()])[0]
+    assert no_probs['allowed']
+
+    
 # EOF