diff --git a/.travis.yml b/.travis.yml
index 313660f..873d54b 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -8,7 +8,6 @@ sudo: false
 env:
     - TOX_ENV=py27-flake8
     - TOX_ENV=py27
-    - TOX_ENV=py33
     - TOX_ENV=py34
     - TOX_ENV=py35
 
diff --git a/dotenv.py b/dotenv.py
index 3b0b2ae..09f01a5 100644
--- a/dotenv.py
+++ b/dotenv.py
@@ -4,7 +4,7 @@
 import warnings
 
 
-__version__ = '1.4.1'
+__version__ = '1.4.2'
 
 
 line_re = re.compile(r"""
@@ -34,12 +34,17 @@
 """, re.IGNORECASE | re.VERBOSE)
 
 
-def read_dotenv(dotenv=None):
+def read_dotenv(dotenv=None, override=False):
     """
     Read a .env file into os.environ.
 
     If not given a path to a dotenv path, does filthy magic stack backtracking
     to find manage.py and then find the dotenv.
+
+    If tests rely on .env files, setting the overwrite flag to True is a safe
+    way to ensure tests run consistently across all environments.
+
+    :param override: True if values in .env should override system variables.
     """
     if dotenv is None:
         frame_filename = sys._getframe().f_back.f_code.co_filename
@@ -51,7 +56,10 @@ def read_dotenv(dotenv=None):
     if os.path.exists(dotenv):
         with open(dotenv) as f:
             for k, v in parse_dotenv(f.read()).items():
-                os.environ.setdefault(k, v)
+                if override:
+                    os.environ[k] = v
+                else:
+                    os.environ.setdefault(k, v)
     else:
         warnings.warn("Not reading {0} - it doesn't exist.".format(dotenv),
                       stacklevel=2)
diff --git a/setup.py b/setup.py
index f35ad7e..e482bcb 100644
--- a/setup.py
+++ b/setup.py
@@ -49,7 +49,6 @@ def get_version(module):
         'Programming Language :: Python :: 2.7',
         'Programming Language :: Python :: 3',
         'Programming Language :: Python :: 3.2',
-        'Programming Language :: Python :: 3.3',
         'Programming Language :: Python :: 3.4',
         'Topic :: Internet :: WWW/HTTP',
     ]
diff --git a/tox.ini b/tox.ini
index 067966f..2bba69b 100644
--- a/tox.ini
+++ b/tox.ini
@@ -1,7 +1,7 @@
 [tox]
 envlist =
     py27-flake8,
-    py27, py32, py33, py34, py35
+    py27, py32, py34, py35
 
 [testenv]
 commands = python setup.py test