diff --git a/tests/unit/test_zpa_policies.py b/tests/unit/test_zpa_policies.py
new file mode 100644
index 00000000..b82afe7b
--- /dev/null
+++ b/tests/unit/test_zpa_policies.py
@@ -0,0 +1,50 @@
+"""
+Unit tests for ZPA Policy Set Controller rule updates.
+
+Tests that a partial update which omits the optional ``action`` keyword
+is still sent to the API instead of raising ``AttributeError``.
+"""
+
+from unittest.mock import Mock
+
+import pytest
+
+from zscaler.zpa.policies import PolicySetControllerAPI
+
+CUSTOMER_ID = "72058304855090128"
+POLICY_SET_ID = "72058304855090130"
+RULE_ID = "72058304855090129"
+
+
+def build_api():
+    """Return a PolicySetControllerAPI and the request executor it was given."""
+    policy_set = Mock()
+    policy_set.get_body.return_value = {"id": POLICY_SET_ID}
+
+    mock_executor = Mock()
+    mock_executor.create_request.return_value = ({}, None)
+    # First execute() resolves the policy set, the second performs the rule update.
+    mock_executor.execute.side_effect = [(policy_set, None), (None, None)]
+
+    return PolicySetControllerAPI(mock_executor, {"client": {"customerId": CUSTOMER_ID}}), mock_executor
+
+
+class TestUpdateIsolationRuleWithoutAction:
+    """Test update_isolation_rule and update_isolation_rule_v2 partial updates."""
+
+    @pytest.mark.parametrize("method_name", ["update_isolation_rule", "update_isolation_rule_v2"])
+    def test_update_without_action_sends_request(self, method_name):
+        """Test omitting the optional action keyword still issues the update request."""
+        # Setup
+        api, mock_executor = build_api()
+
+        # Test
+        rule, _, error = getattr(api, method_name)(rule_id=RULE_ID, description="partial update")
+
+        # Assertions
+        assert error is None
+        assert rule.id == RULE_ID
+
+        payload = mock_executor.create_request.call_args.kwargs["body"]
+        assert payload["action"] is None
+        assert payload["description"] == "partial update"
diff --git a/zscaler/zpa/policies.py b/zscaler/zpa/policies.py
index 64b9c5ed..0a0da29b 100644
--- a/zscaler/zpa/policies.py
+++ b/zscaler/zpa/policies.py
@@ -1305,7 +1305,7 @@ def update_isolation_rule(
             "name": name,
             "description": kwargs.get("description"),
             "rule_order": kwargs.get("rule_order"),
-            "action": action.upper(),
+            "action": action.upper() if action else None,
             "zpnIsolationProfileId": zpn_isolation_profile_id,
             "conditions": self._create_conditions_v1(kwargs.pop("conditions", [])),
         }
@@ -2520,7 +2520,7 @@ def update_isolation_rule_v2(
             "name": name,
             "description": kwargs.get("description"),
             "rule_order": kwargs.get("rule_order"),
-            "action": action.upper(),
+            "action": action.upper() if action else None,
             "zpnIsolationProfileId": zpn_isolation_profile_id,
             "conditions": self._create_conditions_v2(kwargs.pop("conditions", [])),
         }