diff --git a/stix2/core.py b/stix2/core.py
index 81dd492..be2a53d 100644
--- a/stix2/core.py
+++ b/stix2/core.py
@@ -1,5 +1,6 @@
 """STIX 2.0 Objects that are neither SDOs nor SROs"""
 
+from collections import OrderedDict
 
 from . import exceptions
 from .base import _STIXBase
@@ -31,12 +32,13 @@ class STIXObjectProperty(Property):
 class Bundle(_STIXBase):
 
     _type = 'bundle'
-    _properties = {
-        'type': TypeProperty(_type),
-        'id': IDProperty(_type),
-        'spec_version': Property(fixed="2.0"),
-        'objects': ListProperty(STIXObjectProperty),
-    }
+    _properties = OrderedDict()
+    _properties.update([
+        ('type', TypeProperty(_type)),
+        ('id', IDProperty(_type)),
+        ('spec_version', Property(fixed="2.0")),
+        ('objects', ListProperty(STIXObjectProperty)),
+    ])
 
     def __init__(self, *args, **kwargs):
         # Add any positional arguments to the 'objects' kwarg.
diff --git a/stix2/sro.py b/stix2/sro.py
index cf26c32..23f0dd0 100644
--- a/stix2/sro.py
+++ b/stix2/sro.py
@@ -3,7 +3,7 @@
 from collections import OrderedDict
 
 from .base import _STIXBase
-from .other import ExternalReference, GranularMarking
+from .common import ExternalReference, GranularMarking
 from .properties import (BooleanProperty, IDProperty, IntegerProperty, ListProperty,
                          ReferenceProperty, StringProperty, TimestampProperty,
                          TypeProperty)