diff --git a/twilio/rest/resources/base.py b/twilio/rest/resources/base.py
index 9db578b05a..0b9e1f5934 100644
--- a/twilio/rest/resources/base.py
+++ b/twilio/rest/resources/base.py
@@ -177,7 +177,7 @@ def load(self, entries):
             del entries["uri"]
 
         for key in entries.keys():
-            if key.startswith("date_") and isinstance(entries[key], str):
+            if key.startswith("date_") and isinstance(entries[key], string_types):
                 entries[key] = parse_rfc2822_date(entries[key])
 
         self.__dict__.update(entries)