diff --git a/sqlalchemy_utils/functions/batch_fetch.py b/sqlalchemy_utils/functions/batch_fetch.py
index dd28f3c..6b0430e 100644
--- a/sqlalchemy_utils/functions/batch_fetch.py
+++ b/sqlalchemy_utils/functions/batch_fetch.py
@@ -54,6 +54,8 @@ class Path(object):
                 for entity in entities:
                     related_entities.extend(getattr(entity, attrs[0]))
 
+                if not related_entities:
+                    return
                 subpath = '.'.join(attrs[1:])
                 return Path.parse(related_entities, subpath, populate_backrefs)
             else:
@@ -146,8 +148,9 @@ def batch_fetch(entities, *attr_paths):
     if entities:
         for path in attr_paths:
             fetcher = fetcher_factory(entities, path)
-            fetcher.fetch()
-            fetcher.populate()
+            if fetcher:
+                fetcher.fetch()
+                fetcher.populate()
 
 
 def fetcher_factory(entities, path):
@@ -159,13 +162,17 @@ def fetcher_factory(entities, path):
     if isinstance(path, CompositePath):
         fetchers = []
         for path in path.paths:
-            fetchers.append(
-                Path.parse(entities, path, populate_backrefs).fetcher
-            )
+            path = Path.parse(entities, path, populate_backrefs)
+            if path:
+                fetchers.append(
+                    path.fetcher
+                )
 
         return CompositeFetcher(*fetchers)
     else:
-        return Path.parse(entities, path, populate_backrefs).fetcher
+        path = Path.parse(entities, path, populate_backrefs)
+        if path:
+            return path.fetcher
 
 
 class CompositeFetcher(object):
diff --git a/sqlalchemy_utils/types/weekdays.py b/sqlalchemy_utils/types/weekdays.py
index 6e4a1c3..7da314e 100644
--- a/sqlalchemy_utils/types/weekdays.py
+++ b/sqlalchemy_utils/types/weekdays.py
@@ -1,7 +1,7 @@
 # -*- coding: utf-8 -*-
-import six
 from sqlalchemy import types
 from sqlalchemy.dialects.postgresql import BIT
+import six
 get_day_names = None
 try:
     from babel.dates import get_day_names
@@ -75,7 +75,7 @@ class WeekDay(object):
 
 class WeekDays(object):
     def __init__(self, bit_string_or_week_days):
-        if isinstance(bit_string_or_week_days, six.text_type):
+        if isinstance(bit_string_or_week_days, six.string_types):
             self._days = set()
 
             if len(bit_string_or_week_days) != WeekDay.NUM_WEEK_DAYS:
@@ -100,7 +100,7 @@ class WeekDays(object):
     def __eq__(self, other):
         if isinstance(other, WeekDays):
             return self._days == other._days
-        elif isinstance(other, six.text_type):
+        elif isinstance(other, six.string_types):
             return self.as_bit_string() == other
         else:
             return NotImplemented
@@ -138,7 +138,7 @@ class WeekDaysType(types.TypeDecorator):
         if isinstance(value, WeekDays):
             return value.as_bit_string()
 
-        if isinstance(value, six.text_type):
+        if isinstance(value, six.string_types):
             return value
 
     def process_result_value(self, value, dialect):