diff --git a/keep/api/models/alert.py b/keep/api/models/alert.py
index 51f30a4e7d..d6f5ac341a 100644
--- a/keep/api/models/alert.py
+++ b/keep/api/models/alert.py
@@ -78,7 +78,7 @@ class AlertDto(BaseModel):
     firingStartTimeSinceLastResolved: str | None = None
     firingCounter: int = 0
     unresolvedCounter: int = 0
-    environment: str = "undefined"
+    environment: str | None = None
     isFullDuplicate: bool | None = False
     isPartialDuplicate: bool | None = False
     duplicateReason: str | None = None
diff --git a/tests/test_alert_dto.py b/tests/test_alert_dto.py
index 789eb4763b..09a3a4100c 100644
--- a/tests/test_alert_dto.py
+++ b/tests/test_alert_dto.py
@@ -262,3 +262,22 @@ def test_alert_dismiss_forever():
     with freezegun.freeze_time(now + timedelta(days=365)):
         revalidated_alert = AlertDto(**alert.dict())
         assert revalidated_alert.dismissed is True
+
+
+def test_alert_dto_environment_default_is_none():
+    """environment should default to None, not a literal string like 'undefined'."""
+    alert = create_basic_alert(
+        name="Env Default Test",
+        last_received="2024-01-01T00:00:00.000Z",
+    )
+    assert alert.environment is None
+
+
+def test_alert_dto_environment_explicit_value():
+    """Explicitly set environment should be preserved."""
+    alert = create_basic_alert(
+        name="Env Explicit Test",
+        last_received="2024-01-01T00:00:00.000Z",
+        environment="production",
+    )
+    assert alert.environment == "production"
diff --git a/tests/test_iohandler.py b/tests/test_iohandler.py
index 0f1c9dcaed..e902fe1344 100644
--- a/tests/test_iohandler.py
+++ b/tests/test_iohandler.py
@@ -1038,6 +1038,16 @@ def test_fn_na_on_missing_key(mocked_context_manager):
     assert result == "ts=N/A", f"Expected 'ts=N/A', got '{result}'"
 
 
+def test_fn_na_on_none_environment(mocked_context_manager):
+    """fn.na renders 'N/A' when environment is absent (defaults to None, not 'undefined')."""
+    mocked_context_manager.get_full_context.return_value = {
+        "alert": {"name": "test-alert"},  # no 'environment' field
+    }
+    iohandler = IOHandler(mocked_context_manager)
+    result = iohandler.render("env={{#fn.na}}{{ alert.environment }}{{/fn.na}}")
+    assert result == "env=N/A", f"Expected 'env=N/A', got '{result}'"
+
+
 def test_fn_default_on_missing_key(mocked_context_manager):
     """fn.default renders an empty string when the wrapped field is absent."""
     mocked_context_manager.get_full_context.return_value = {