diff --git a/stix2/__init__.py b/stix2/__init__.py
index b3c2f5b..920a259 100644
--- a/stix2/__init__.py
+++ b/stix2/__init__.py
@@ -4,11 +4,12 @@
 
 from . import exceptions
 from .bundle import Bundle
-from .observables import (URL, Artifact, AutonomousSystem, Directory,
-                          DomainName, EmailAddress, EmailMessage, EmailMIMEComponent, File,
-                          IPv4Address, IPv6Address, MACAddress, Mutex,
-                          NetworkTraffic, Process, Software, UserAccount,
-                          WindowsRegistryKey, WindowsRegistryValueType, X509Certificate)
+from .observables import (URL, ArchiveExt, Artifact, AutonomousSystem,
+                          Directory, DomainName, EmailAddress, EmailMessage,
+                          EmailMIMEComponent, File, IPv4Address, IPv6Address,
+                          MACAddress, Mutex, NetworkTraffic, Process, Software,
+                          UserAccount, WindowsRegistryKey,
+                          WindowsRegistryValueType, X509Certificate)
 from .other import (ExternalReference, GranularMarking, KillChainPhase,
                     MarkingDefinition, StatementMarking, TLPMarking)
 from .sdo import (AttackPattern, Campaign, CourseOfAction, Identity, Indicator,
@@ -56,6 +57,14 @@ OBJ_MAP_OBSERVABLE = {
     'x509-certificate': X509Certificate,
 }
 
+EXT_MAP_FILE = {
+    'archive-ext': ArchiveExt,
+}
+
+EXT_MAP = {
+    'file': EXT_MAP_FILE,
+}
+
 
 def parse(data):
     """Deserialize a string or file-like object into a STIX object"""
@@ -89,6 +98,14 @@ def parse_observable(data, _valid_refs):
     try:
         obj_class = OBJ_MAP_OBSERVABLE[obj['type']]
     except KeyError:
-        # TODO handle custom objects
+        # TODO handle custom observable objects
         raise ValueError("Can't parse unknown object type '%s'!" % obj['type'])
+
+    if 'extensions' in obj and obj['type'] in EXT_MAP:
+        for name, ext in obj['extensions'].items():
+            if name not in EXT_MAP[obj['type']]:
+                raise ValueError("Can't parse Unknown extension type '%s' for object type '%s'!" % (name, obj['type']))
+            ext_class = EXT_MAP[obj['type']][name]
+            obj['extensions'][name] = ext_class(**obj['extensions'][name])
+
     return obj_class(**obj)
diff --git a/stix2/observables.py b/stix2/observables.py
index 0835d5b..d724aec 100644
--- a/stix2/observables.py
+++ b/stix2/observables.py
@@ -7,7 +7,7 @@ and do not have a '_type' attribute.
 
 from .base import _Observable, _STIXBase
 from .properties import (BinaryProperty, BooleanProperty, DictionaryProperty,
-                         EmbeddedObjectProperty, EnumProperty, HashesProperty,
+                         EmbeddedObjectProperty, EnumProperty, ExtensionsProperty, HashesProperty,
                          HexProperty, IntegerProperty, ListProperty,
                          ObjectReferenceProperty, StringProperty,
                          TimestampProperty, TypeProperty)
@@ -111,11 +111,19 @@ class EmailMessage(_Observable):
         # self._dependency(["is_multipart"], ["body"], [False])
 
 
+class ArchiveExt(_STIXBase):
+    _properties = {
+        'contains_refs': ListProperty(ObjectReferenceProperty, required=True),
+        'version': StringProperty(),
+        'comment': StringProperty(),
+    }
+
+
 class File(_Observable):
     _type = 'file'
     _properties = {
         'type': TypeProperty(_type),
-        # extensions
+        'extensions': ExtensionsProperty(),
         'hashes': HashesProperty(),
         'size': IntegerProperty(),
         'name': StringProperty(),
diff --git a/stix2/properties.py b/stix2/properties.py
index 74d0856..c8674ef 100644
--- a/stix2/properties.py
+++ b/stix2/properties.py
@@ -376,3 +376,7 @@ class EnumProperty(StringProperty):
         if value not in self.allowed:
             raise ValueError("value '%s' is not valid for this enumeration." % value)
         return self.string_type(value)
+
+
+class ExtensionsProperty(DictionaryProperty):
+    pass
diff --git a/stix2/test/test_observed_data.py b/stix2/test/test_observed_data.py
index a1ff653..475efe7 100644
--- a/stix2/test/test_observed_data.py
+++ b/stix2/test/test_observed_data.py
@@ -281,6 +281,50 @@ def test_parse_email_message(data):
     assert odata.body_multipart[0].content_disposition == "inline"
 
 
+@pytest.mark.parametrize("data", [
+    """"0": {
+            "type": "file",
+            "hashes": {
+                "SHA-256": "ceafbfd424be2ca4a5f0402cae090dda2fb0526cf521b60b60077c0f622b285a"
+            }
+        },
+        "1": {
+            "type": "file",
+            "hashes": {
+                "SHA-256": "19c549ec2628b989382f6b280cbd7bb836a0b461332c0fe53511ce7d584b89d3"
+            }
+        },
+        "2": {
+            "type": "file",
+            "hashes": {
+                "SHA-256": "0969de02ecf8a5f003e3f6d063d848c8a193aada092623f8ce408c15bcb5f038"
+            }
+        },
+        "3": {
+            "type": "file",
+            "name": "foo.zip",
+            "hashes": {
+                "SHA-256": "35a01331e9ad96f751278b891b6ea09699806faedfa237d40513d92ad1b7100f"
+            },
+            "mime_type": "application/zip",
+            "extensions": {
+                "archive-ext": {
+                    "contains_refs": [
+                        "0",
+                        "1",
+                        "2"
+                    ],
+                    "version": "5.0"
+                }
+            }
+        }""",
+])
+def test_parse_file_archive(data):
+    odata_str = re.compile('"objects".+\},', re.DOTALL).sub('"objects": { %s },' % data, EXPECTED)
+    odata = stix2.parse(odata_str)
+    assert odata.objects["3"].extensions['archive-ext'].version == "5.0"
+
+
 @pytest.mark.parametrize("data", [
     """
     {