diff --git a/stix2/v21/sdo.py b/stix2/v21/sdo.py
index 7685401..be6da3a 100644
--- a/stix2/v21/sdo.py
+++ b/stix2/v21/sdo.py
@@ -107,6 +107,8 @@ class CourseOfAction(STIXDomainObject):
         ('description', StringProperty()),
         ('revoked', BooleanProperty(default=lambda: False)),
         ('labels', ListProperty(StringProperty)),
+        ('confidence', IntegerProperty()),
+        ('lang', StringProperty()),
         ('external_references', ListProperty(ExternalReference)),
         ('object_marking_refs', ListProperty(ReferenceProperty(valid_types='marking-definition', spec_version='2.1'))),
         ('granular_markings', ListProperty(GranularMarking)),