diff --git a/board/safety/safety_chrysler.h b/board/safety/safety_chrysler.h
index c4e26cf46f8237..8c897115513567 100644
--- a/board/safety/safety_chrysler.h
+++ b/board/safety/safety_chrysler.h
@@ -102,12 +102,13 @@ static int chrysler_tx_hook(CAN_FIFOMailBox_TypeDef *to_send) {
     }
   }
 
-  // FORCE CANCEL: safety check only relevant when spamming the cancel button.
-  // ensuring that only the cancel button press is sent when controls are off.
-  // This avoids unintended engagements while still allowing resume spam
-  // TODO!
+  // FORCE CANCEL: only the cancel button press is allowed
+  if (addr == 571) {
+    if (GET_BYTE(to_send, 0) != 1) {
+      tx = 0;
+    }
+  }
 
-  // 1 allows the message through
   return tx;
 }
 
diff --git a/tests/safety/test_chrysler.py b/tests/safety/test_chrysler.py
index de3e5ae08f239c..2ddd3aff8ac06a 100755
--- a/tests/safety/test_chrysler.py
+++ b/tests/safety/test_chrysler.py
@@ -16,23 +16,6 @@
 
 TX_MSGS = [[571, 0], [658, 0], [678, 0]]
 
-def twos_comp(val, bits):
-  if val >= 0:
-    return val
-  else:
-    return (2**bits) + val
-
-def sign(a):
-  if a > 0:
-    return 1
-  else:
-    return -1
-
-def swap_bytes(data_str):
-  """Accepts string with hex, returns integer with order swapped for CAN."""
-  a = int(data_str, 16)
-  return ((a & 0xff) << 24) + ((a & 0xff00) << 8) + ((a & 0x00ff0000) >> 8) + ((a & 0xff000000) >> 24)
-
 class TestChryslerSafety(unittest.TestCase):
   @classmethod
   def setUp(cls):
@@ -42,7 +25,7 @@ def setUp(cls):
 
   def _button_msg(self, buttons):
     to_send = libpandasafety_py.ffi.new('CAN_FIFOMailBox_TypeDef *')
-    to_send[0].RIR = 1265 << 21
+    to_send[0].RIR = 571 << 21
     to_send[0].RDLR = buttons
     return to_send
 
@@ -178,6 +161,14 @@ def test_torque_measurements(self):
     self.assertEqual(0, self.safety.get_chrysler_torque_meas_max())
     self.assertEqual(0, self.safety.get_chrysler_torque_meas_min())
 
+  def test_cancel_button(self):
+    CANCEL = 1
+    for b in range(0, 0xff):
+      if b == CANCEL:
+        self.assertTrue(self.safety.safety_tx_hook(self._button_msg(b)))
+      else:
+        self.assertFalse(self.safety.safety_tx_hook(self._button_msg(b)))
+
   def test_fwd_hook(self):
     buss = list(range(0x0, 0x3))
     msgs = list(range(0x1, 0x800))