diff --git a/releases/ChangeLog.md b/releases/ChangeLog.md
index 473558e3..fecd60e0 100644
--- a/releases/ChangeLog.md
+++ b/releases/ChangeLog.md
@@ -5,6 +5,12 @@
 - Enhancement: Promoted the address explorer to the main menu. It's useful!
 - Bugfix: zero-length BIP39 passphrase, when saved, would cause a crash when
   restore attempted. We recommend longer passphrases, but fixed the issue.
+- Enhancement: Move the "blockchain" setting deep into the "Danger Zone" and add
+  warning screen. This mitigates a concern raised by @benma (Marko Bencun) where
+  an attacker could socially-engineer you to sign a transaction on Testnet, which
+  corresponds to UTXO on main net being stolen. Only developers should be using
+  Testnet anyway.
+
 
 ## 3.1.9 - Aug 6, 2020
 
diff --git a/shared/actions.py b/shared/actions.py
index 743f800a..703c80f3 100644
--- a/shared/actions.py
+++ b/shared/actions.py
@@ -426,6 +426,18 @@ async def pick_scramble(*a):
     from menu import start_chooser
     start_chooser(scramble_keypad_chooser)
 
+async def confirm_testnet_mode(*a):
+    from choosers import chain_chooser
+    from menu import start_chooser
+    from chains import current_chain
+
+    if settings.get('chain') != 'XTN':
+        if not await ux_confirm("Testnet must only be used by developers because \
+correctly- crafted transactions signed on Testnet could be broadcast on Mainnet."):
+            return
+
+    start_chooser(chain_chooser)
+
 async def pick_inputs_delete(*a):
     # Setting: delete input PSBT
     if await ux_show_story('''\
diff --git a/shared/auth.py b/shared/auth.py
index ac1669de..d8018a7f 100644
--- a/shared/auth.py
+++ b/shared/auth.py
@@ -939,8 +939,7 @@ async def interact(self):
 
 
 def start_bip39_passphrase(pw):
-    # tell the local user the secret words, and then save to SPI flash
-    # USB caller has to come back and download encrypted contents.
+    # new passphrase has come in via USB. offer to switch to it.
 
     UserAuthorizedAction.cleanup()
     UserAuthorizedAction.active_request = NewPassphrase(pw)
diff --git a/shared/choosers.py b/shared/choosers.py
index 87f77bca..f87a1cd7 100644
--- a/shared/choosers.py
+++ b/shared/choosers.py
@@ -81,6 +81,7 @@ def set_login_countdown(idx, text):
 
 
 def chain_chooser():
+    # Pick Bitcoin or Testnet3 blockchains
     from chains import AllChains
 
     chain = settings.get('chain', 'BTC')
diff --git a/shared/flow.py b/shared/flow.py
index 1eff73a7..f5371fb4 100644
--- a/shared/flow.py
+++ b/shared/flow.py
@@ -63,7 +63,6 @@ def has_secrets():
     MenuItem('Set Nickname', f=pick_nickname),
     MenuItem('Scramble Keypad', f=pick_scramble),
     MenuItem('Delete PSBTs', f=pick_inputs_delete),
-    MenuItem('Blockchain', chooser=chain_chooser),
 ]
 
 WalletExportMenu = [  
@@ -143,6 +142,7 @@ def has_secrets():
     MenuItem("Set High-Water", f=set_highwater),
     MenuItem('Wipe HSM Policy', f=wipe_hsm_policy, predicate=hsm_policy_available),
     MenuItem('Clear OV cache', f=wipe_ovc),
+    MenuItem('Testnet Mode', f=confirm_testnet_mode),
     MenuItem('Settings space', f=show_settings_space),
 ]
 
diff --git a/shared/menu.py b/shared/menu.py
index c63e3e1f..c6714de2 100644
--- a/shared/menu.py
+++ b/shared/menu.py
@@ -16,7 +16,7 @@ def start_chooser(chooser):
     # get which one to show as selected, list of choices, and fcn to call after
     selected, choices, setter = chooser()
 
-    def picked(menu, picked, xx_self):
+    async def picked(menu, picked, xx_self):
         menu.chosen = picked
         menu.show()
         await sleep_ms(100)     # visual feedback that we changed it
diff --git a/testing/test_pwsave.py b/testing/test_pwsave.py
index 70228eae..38da6bb9 100644
--- a/testing/test_pwsave.py
+++ b/testing/test_pwsave.py
@@ -43,6 +43,7 @@ def doit():
         'aBc1 aBc2 aBc3', 
         'abcd defg',
         '1aaa 2aaa',
+        '1aaa2aaa',
         'ab'*25,
     ])
 def test_first_time(pws, need_keypress, cap_story, pick_menu_item, goto_home, enter_complex, cap_menu, get_to_pwmenu):
diff --git a/testing/test_sign.py b/testing/test_sign.py
index 3a06428c..de03d668 100644
--- a/testing/test_sign.py
+++ b/testing/test_sign.py
@@ -309,10 +309,11 @@ def EncodeDecimal(o):
         network = a2b_hex(resp['hex'])
 
         # assert resp['complete']
-        #print("Final txn: %r" % network)
+        print("Final txn: %r" % network)
         open('debug/finalized-by-btcd.txn', 'wb').write(network)
 
         # try to send it
+        assert 0
         txed = bitcoind.sendrawtransaction(B2A(network))
         print("Final txn hash: %r" % txed)
 
@@ -321,6 +322,7 @@ def EncodeDecimal(o):
         #print("Final txn: %s" % B2A(signed))
         open('debug/finalized-by-cc.txn', 'wb').write(signed)
 
+        assert 0
         txed = bitcoind.sendrawtransaction(B2A(signed))
         print("Final txn hash: %r" % txed)