diff --git a/README.rst b/README.rst
index 3211c0f..3fef861 100644
--- a/README.rst
+++ b/README.rst
@@ -1,7 +1,7 @@
 nested_lookup
 #############
 
-.. image:: https://img.shields.io/badge/pypi-0.2.15-green.svg
+.. image:: https://img.shields.io/badge/pypi-0.2.16-green.svg
   :target: https://pypi.python.org/pypi/nested-lookup
 .. image:: https://travis-ci.org/rameshrvr/nested-lookup.svg?branch=master
   :target: https://travis-ci.org/rameshrvr/nested-lookup
diff --git a/nested_lookup/nested_lookup.py b/nested_lookup/nested_lookup.py
index f61d66e..698718a 100644
--- a/nested_lookup/nested_lookup.py
+++ b/nested_lookup/nested_lookup.py
@@ -13,6 +13,11 @@ def nested_lookup(key, document, wild=False, with_keys=False):
     return list(_nested_lookup(key, document, wild=wild, with_keys=with_keys))
 
 
+def _is_case_insensitive_substring(a, b):
+    """return True if `a` is a case insensitive substring of `b`, else False"""
+    return isinstance(a, str) and isinstance(b, str) and a.lower() in b.lower()
+
+
 def _nested_lookup(key, document, wild=False, with_keys=False):
     """Lookup a key in a nested document, yield a value"""
     if isinstance(document, list):
@@ -22,7 +27,7 @@ def _nested_lookup(key, document, wild=False, with_keys=False):
 
     if isinstance(document, dict):
         for k, v in iteritems(document):
-            if key == k or (wild and key.lower() in k.lower()):
+            if key == k or (wild and _is_case_insensitive_substring(key, k)):
                 if with_keys:
                     yield k, v
                 else:
diff --git a/setup.py b/setup.py
index 9d53994..ea930e8 100644
--- a/setup.py
+++ b/setup.py
@@ -17,7 +17,7 @@ with open("requirements.txt", "r") as f:
 
 setup(
     name="nested-lookup",
-    version="0.2.15",
+    version="0.2.16",
     description="Python functions for working with deeply nested documents (lists and dicts) ",
     keywords="nested document dictionary dict list lookup schema json xml yaml",
     long_description=open("README.rst").read(),
@@ -45,6 +45,4 @@ setup(
 # build package:
 # pip install twine
 # python setup.py sdist
-
-# built and uploaded to pypi with this:
-# python setup.py sdist bdist_egg register upload
+# twine upload dist/*
diff --git a/test_nested_lookup.py b/test_nested_lookup.py
index 7a8b8e1..32e9a57 100644
--- a/test_nested_lookup.py
+++ b/test_nested_lookup.py
@@ -38,6 +38,7 @@ class TestNestedLookup(TestCase):
             "name": "Test",
             "date": "YYYY-MM-DD HH:MM:SS",
         }
+        self.subject_dict4 = {1: "a", 2: {"b": 44, "C": 55}, 3: "d", 4: "e"}
 
     def test_nested_lookup(self):
         results = nested_lookup("d", self.subject_dict)
@@ -74,6 +75,10 @@ class TestNestedLookup(TestCase):
         self.assertIn("test2@example.com", results)
         self.assertIn("test3@example.com", results)
 
+        # test that wild works with a document that has integers as keys.
+        results = nested_lookup(key="c", document=self.subject_dict4, wild=True)
+        self.assertIn(55, results)
+
     def test_wild_with_keys_nested_lookup(self):
         matches = nested_lookup(
             key="mail", document=self.subject_dict2, wild=True, with_keys=True