diff --git a/gunicorn/pidfile.py b/gunicorn/pidfile.py
index 7f7f844f..a6e085fd 100644
--- a/gunicorn/pidfile.py
+++ b/gunicorn/pidfile.py
@@ -75,6 +75,8 @@ class Pidfile(object):
                     os.kill(wpid, 0)
                     return wpid
                 except OSError as e:
+                    if e.args[0] == errno.EPERM:
+                        return wpid
                     if e.args[0] == errno.ESRCH:
                         return
                     raise
diff --git a/tests/test_pidfile.py b/tests/test_pidfile.py
new file mode 100644
index 00000000..54936cac
--- /dev/null
+++ b/tests/test_pidfile.py
@@ -0,0 +1,59 @@
+# -*- coding: utf-8 -
+#
+# This file is part of gunicorn released under the MIT license.
+# See the NOTICE for more information.
+
+import errno
+import sys
+
+try:
+    import unittest.mock as mock
+except ImportError:
+    import mock
+
+import gunicorn.pidfile
+
+
+def builtin(name):
+    if sys.version_info >= (3, 0):
+        module = 'builtins'
+    else:
+        module = '__builtin__'
+
+    return '{0}.{1}'.format(module, name)
+
+
+@mock.patch(builtin('open'), new_callable=mock.mock_open)
+def test_validate_no_file(_open):
+    pidfile = gunicorn.pidfile.Pidfile('test.pid')
+    _open.side_effect = IOError(errno.ENOENT)
+    assert pidfile.validate() is None
+
+
+@mock.patch(builtin('open'), new_callable=mock.mock_open, read_data='1')
+@mock.patch('os.kill')
+def test_validate_file_pid_exists(kill, _open):
+    pidfile = gunicorn.pidfile.Pidfile('test.pid')
+    assert pidfile.validate() == 1
+
+
+@mock.patch(builtin('open'), new_callable=mock.mock_open, read_data='a')
+def test_validate_file_pid_malformed(_open):
+    pidfile = gunicorn.pidfile.Pidfile('test.pid')
+    assert pidfile.validate() is None
+
+
+@mock.patch(builtin('open'), new_callable=mock.mock_open, read_data='1')
+@mock.patch('os.kill')
+def test_validate_file_pid_exists_kill_exception(kill, _open):
+    pidfile = gunicorn.pidfile.Pidfile('test.pid')
+    kill.side_effect = OSError(errno.EPERM)
+    assert pidfile.validate() == 1
+
+
+@mock.patch(builtin('open'), new_callable=mock.mock_open, read_data='1')
+@mock.patch('os.kill')
+def test_validate_file_pid_does_not_exist(kill, _open):
+    pidfile = gunicorn.pidfile.Pidfile('test.pid')
+    kill.side_effect = OSError(errno.ESRCH)
+    assert pidfile.validate() is None