diff --git a/stix2/v20/__init__.py b/stix2/v20/__init__.py
index 36d09be..002343b 100644
--- a/stix2/v20/__init__.py
+++ b/stix2/v20/__init__.py
@@ -32,7 +32,7 @@ from .observables import (
     UNIXAccountExt, UserAccount, WindowsPEBinaryExt,
     WindowsPEOptionalHeaderType, WindowsPESection, WindowsProcessExt,
     WindowsRegistryKey, WindowsRegistryValueType, WindowsServiceExt,
-    X509Certificate, X509V3ExtenstionsType,
+    X509Certificate, X509V3ExtensionsType,
 )
 from .sdo import (
     AttackPattern, Campaign, CourseOfAction, CustomObject, Identity, Indicator,
@@ -123,7 +123,7 @@ __all__ = """
     UNIXAccountExt, UserAccount, WindowsPEBinaryExt,
     WindowsPEOptionalHeaderType, WindowsPESection, WindowsProcessExt,
     WindowsRegistryKey, WindowsRegistryValueType, WindowsServiceExt,
-    X509Certificate, X509V3ExtenstionsType,
+    X509Certificate, X509V3ExtensionsType,
 
     AttackPattern, Campaign, CourseOfAction, CustomObject, Identity, Indicator,
     IntrusionSet, Malware, ObservedData, Report, ThreatActor, Tool,
diff --git a/stix2/v20/observables.py b/stix2/v20/observables.py
index 79d4e79..cec979e 100644
--- a/stix2/v20/observables.py
+++ b/stix2/v20/observables.py
@@ -724,7 +724,7 @@ class WindowsRegistryKey(_Observable):
     ])
 
 
-class X509V3ExtenstionsType(_STIXBase20):
+class X509V3ExtensionsType(_STIXBase20):
     """For more detailed information on this object's properties, see
     `the STIX 2.0 specification <http://docs.oasis-open.org/cti/stix/v2.0/cs01/part4-cyber-observable-objects/stix-v2.0-cs01-part4-cyber-observable-objects.html#_Toc496716298>`__.
     """  # noqa
@@ -770,7 +770,7 @@ class X509Certificate(_Observable):
         ('subject_public_key_algorithm', StringProperty()),
         ('subject_public_key_modulus', StringProperty()),
         ('subject_public_key_exponent', IntegerProperty()),
-        ('x509_v3_extensions', EmbeddedObjectProperty(type=X509V3ExtenstionsType)),
+        ('x509_v3_extensions', EmbeddedObjectProperty(type=X509V3ExtensionsType)),
         ('extensions', ExtensionsProperty(spec_version="2.0", enclosing_type=_type)),
     ])
 
diff --git a/stix2/v21/__init__.py b/stix2/v21/__init__.py
index 70f2a79..856ff13 100644
--- a/stix2/v21/__init__.py
+++ b/stix2/v21/__init__.py
@@ -32,7 +32,7 @@ from .observables import (
     UNIXAccountExt, UserAccount, WindowsPEBinaryExt,
     WindowsPEOptionalHeaderType, WindowsPESection, WindowsProcessExt,
     WindowsRegistryKey, WindowsRegistryValueType, WindowsServiceExt,
-    X509Certificate, X509V3ExtenstionsType,
+    X509Certificate, X509V3ExtensionsType,
 )
 from .sdo import (
     AttackPattern, Campaign, CourseOfAction, CustomObject, Grouping, Identity,
@@ -132,7 +132,7 @@ __all__ = """
     UNIXAccountExt, UserAccount, WindowsPEBinaryExt,
     WindowsPEOptionalHeaderType, WindowsPESection, WindowsProcessExt,
     WindowsRegistryKey, WindowsRegistryValueType, WindowsServiceExt,
-    X509Certificate, X509V3ExtenstionsType,
+    X509Certificate, X509V3ExtensionsType,
 
     AttackPattern, Campaign, CourseOfAction, CustomObject, Grouping, Identity,
     Indicator, Infrastructure, IntrusionSet, Location, Malware,
diff --git a/stix2/v21/observables.py b/stix2/v21/observables.py
index 7919383..11e1d9f 100644
--- a/stix2/v21/observables.py
+++ b/stix2/v21/observables.py
@@ -851,7 +851,7 @@ class WindowsRegistryKey(_Observable):
     _id_contributing_properties = ["key", "values"]
 
 
-class X509V3ExtenstionsType(_STIXBase21):
+class X509V3ExtensionsType(_STIXBase21):
     """For more detailed information on this object's properties, see
     `the STIX 2.1 specification <https://docs.oasis-open.org/cti/stix/v2.1/cs01/stix-v2.1-cs01.html#_c1kt4dheb6vz>`__.
     """
@@ -899,7 +899,7 @@ class X509Certificate(_Observable):
         ('subject_public_key_algorithm', StringProperty()),
         ('subject_public_key_modulus', StringProperty()),
         ('subject_public_key_exponent', IntegerProperty()),
-        ('x509_v3_extensions', EmbeddedObjectProperty(type=X509V3ExtenstionsType)),
+        ('x509_v3_extensions', EmbeddedObjectProperty(type=X509V3ExtensionsType)),
         ('object_marking_refs', ListProperty(ReferenceProperty(valid_types='marking-definition', spec_version='2.1'))),
         ('granular_markings', ListProperty(GranularMarking)),
         ('defanged', BooleanProperty(default=lambda: False)),