diff --git a/dropbox/stone_base.py b/dropbox/stone_base.py
index 9091a0fb..cdefd988 100644
--- a/dropbox/stone_base.py
+++ b/dropbox/stone_base.py
@@ -13,7 +13,7 @@
 except (SystemError, ValueError):
     # Catch errors raised when importing a relative module when not in a package.
     # This makes testing this file directly (outside of a package) easier.
-    import stone_validators as bv
+    import stone_validators as bv  # type: ignore
 
 
 class Union(object):
diff --git a/dropbox/stone_serializers.py b/dropbox/stone_serializers.py
index 837416dc..23bd6657 100644
--- a/dropbox/stone_serializers.py
+++ b/dropbox/stone_serializers.py
@@ -24,7 +24,7 @@
 except (SystemError, ValueError):
     # Catch errors raised when importing a relative module when not in a package.
     # This makes testing this file directly (outside of a package) easier.
-    import stone_validators as bv
+    import stone_validators as bv  # type: ignore
 
 
 # --------------------------------------------------------------
diff --git a/dropbox/stone_validators.py b/dropbox/stone_validators.py
index f32d7d20..59f8975a 100644
--- a/dropbox/stone_validators.py
+++ b/dropbox/stone_validators.py
@@ -18,6 +18,7 @@
 import numbers
 import re
 import six
+from typing import Optional
 
 if six.PY3:
     _binary_types = (bytes, memoryview)
@@ -121,8 +122,8 @@ class Integer(Primitive):
     Do not use this class directly. Extend it and specify a 'minimum' and
     'maximum' value as class variables for a more restrictive integer range.
     """
-    minimum = None
-    maximum = None
+    minimum = None  # type: Optional[numbers.Integral]
+    maximum = None  # type: Optional[numbers.Integral]
 
     def __init__(self, min_value=None, max_value=None):
         """
@@ -183,8 +184,8 @@ class Real(Primitive):
     and 'maximum' value to enforce a range that's a subset of the Python float
     implementation. Python floats are doubles.
     """
-    minimum = None
-    maximum = None
+    minimum = None  # type: Optional[numbers.Real]
+    maximum = None  # type: Optional[numbers.Real]
 
     def __init__(self, min_value=None, max_value=None):
         """
diff --git a/stone b/stone
index 6356f51c..1824dbe8 160000
--- a/stone
+++ b/stone
@@ -1 +1 @@
-Subproject commit 6356f51cc37d3e5efe8200931531f3988a247eeb
+Subproject commit 1824dbe81167b28ee8ae8a80a26125df5be24bea