diff --git a/sphinx/config.py b/sphinx/config.py
index 12c2a04ba..f76d330ac 100644
--- a/sphinx/config.py
+++ b/sphinx/config.py
@@ -165,7 +165,11 @@ class Config(object):
             try:
                 try:
                     os.chdir(dirname)
-                    execfile(config['__file__'], config)
+                    try:
+                        f = open(config_file, 'U')
+                        exec f in config
+                    finally:
+                        f.close()
                 except SyntaxError, err:
                     raise ConfigError('There is a syntax error in your '
                                       'configuration file: ' + str(err))
diff --git a/tests/test_quickstart.py b/tests/test_quickstart.py
index cb40d27cf..34c54f95a 100644
--- a/tests/test_quickstart.py
+++ b/tests/test_quickstart.py
@@ -85,7 +85,11 @@ def test_quickstart_defaults(tempdir):
     conffile = tempdir / 'conf.py'
     assert conffile.isfile()
     ns = {}
-    execfile(conffile, ns)
+    try:
+        f = open(conffile, 'U')
+        exec f in ns
+    finally:
+        f.close()
     assert ns['extensions'] == []
     assert ns['templates_path'] == ['_templates']
     assert ns['source_suffix'] == '.rst'
@@ -138,7 +142,11 @@ def test_quickstart_all_answers(tempdir):
     conffile = tempdir / 'source' / 'conf.py'
     assert conffile.isfile()
     ns = {}
-    execfile(conffile, ns)
+    try:
+        f = open(conffile, 'U')
+        exec f in ns
+    finally:
+        f.close()
     assert ns['extensions'] == ['sphinx.ext.autodoc', 'sphinx.ext.doctest']
     assert ns['templates_path'] == ['.templates']
     assert ns['source_suffix'] == '.txt'