diff --git a/pysoundfile.py b/pysoundfile.py
index a4a2aa5..105f548 100644
--- a/pysoundfile.py
+++ b/pysoundfile.py
@@ -11,14 +11,10 @@
 __version__ = "0.5.0"
 
 import numpy as _np
+import os as _os
 from cffi import FFI as _FFI
 from os import SEEK_SET, SEEK_CUR, SEEK_END
 
-try:
-    import builtins as _builtins
-except ImportError:
-    import __builtin__ as _builtins  # for Python < 3.0
-
 _ffi = _FFI()
 _ffi.cdef("""
 enum
@@ -563,16 +559,14 @@ def __init__(self, file, mode='r', samplerate=None, channels=None,
             ``seek()`` and ``tell()``).
         mode : {'r', 'r+', 'w', 'w+', 'x', 'x+'}, optional
             Open mode.  Has to begin with one of these three characters:
-            ``'r'`` for reading, ``'w'`` for writing (truncates) or
-            ``'x'`` for writing (but fail if already existing).
-            Additionally, it may contain ``'+'`` to open a file for both
-            reading and writing.
+            ``'r'`` for reading, ``'w'`` for writing (truncates `file`)
+            or ``'x'`` for writing (raises an error if `file` already
+            exists).  Additionally, it may contain ``'+'`` to open
+            `file` for both reading and writing.
             The character ``'b'`` for *binary mode* is implied because
             all sound files have to be opened in this mode.
-
-            .. note:: The modes containing ``'x'`` are only available
-                      since Python 3.3!
-
+            If `file` is a file descriptor or a file-like object,
+            ``'w'`` doesn't truncate and ``'x'`` doesn't raise an error.
         samplerate : int
             The sample rate of the file.  If `mode` contains ``'r'``,
             this is obtained from the file (except for ``'RAW'`` files).
@@ -634,9 +628,9 @@ def __init__(self, file, mode='r', samplerate=None, channels=None,
             raise ValueError("mode must contain exactly one of 'xrw'")
         self._mode = mode
 
-        if '+' in mode:
+        if '+' in modes:
             mode_int = _snd.SFM_RDWR
-        elif 'r' in mode:
+        elif 'r' in modes:
             mode_int = _snd.SFM_READ
         else:
             mode_int = _snd.SFM_WRITE
@@ -645,13 +639,13 @@ def __init__(self, file, mode='r', samplerate=None, channels=None,
         self._name = getattr(file, 'name', file)
         if format is None:
             format = str(self.name).rsplit('.', 1)[-1].upper()
-            if format not in _formats and 'r' not in mode:
+            if format not in _formats and 'r' not in modes:
                 raise TypeError(
                     "No format specified and unable to get format from "
                     "file extension: %s" % repr(self.name))
 
         self._info = _ffi.new("SF_INFO*")
-        if 'r' not in mode or str(format).upper() == 'RAW':
+        if 'r' not in modes or str(format).upper() == 'RAW':
             if samplerate is None:
                 raise TypeError("samplerate must be specified")
             self._info.samplerate = samplerate
@@ -670,11 +664,14 @@ def __init__(self, file, mode='r', samplerate=None, channels=None,
             raise ValueError("closefd=False only allowed for file descriptors")
 
         if isinstance(file, str):
-            if 'b' not in mode:
-                mode += 'b'
-            file = self._filestream = _builtins.open(file, mode, buffering=0)
-
-        if isinstance(file, int):
+            if _os.path.isfile(file):
+                if 'x' in modes:
+                    raise OSError("File exists: %s" % repr(file))
+                elif modes.issuperset('w+'):
+                    # truncate the file, because SFM_RDWR doesn't:
+                    _os.close(_os.open(file, _os.O_WRONLY | _os.O_TRUNC))
+            self._file = _snd.sf_open(file.encode(), mode_int, self._info)
+        elif isinstance(file, int):
             self._file = _snd.sf_open_fd(file, mode_int, self._info, closefd)
         elif all(hasattr(file, a) for a in ('seek', 'read', 'write', 'tell')):
             self._file = _snd.sf_open_virtual(
@@ -719,7 +716,6 @@ def __init__(self, file, mode='r', samplerate=None, channels=None,
 
     # avoid confusion if something goes wrong before assigning self._file:
     _file = None
-    _filestream = None
 
     def __del__(self):
         self.close()
@@ -1007,8 +1003,6 @@ def close(self):
             self.flush()
             err = _snd.sf_close(self._file)
             self._file = None
-            if self._filestream:
-                self._filestream.close()
             self._handle_error_number(err)
 
     def _init_virtual_io(self, file):
diff --git a/tests/test_pysoundfile.py b/tests/test_pysoundfile.py
index bdf302e..1fa6972 100644
--- a/tests/test_pysoundfile.py
+++ b/tests/test_pysoundfile.py
@@ -3,7 +3,6 @@
 import os
 import shutil
 import pytest
-import sys
 
 data_stereo = np.array([[1.0,  -1.0],
                         [0.75, -0.75],
@@ -397,13 +396,28 @@ def test_open_with_mode_is_none():
             assert f.mode == 'rb'
 
 
-@pytest.mark.skipif(sys.version_info < (3, 3),
-                    reason="mode='x' not supported in Python < 3.3")
 def test_open_with_mode_is_x():
-    with pytest.raises(FileExistsError):
+    with pytest.raises(OSError) as excinfo:
         sf.SoundFile(filename_stereo, 'x', 44100, 2)
-    with pytest.raises(FileExistsError):
+    assert "exists" in str(excinfo.value)
+    with pytest.raises(OSError) as excinfo:
         sf.SoundFile(filename_stereo, 'x+', 44100, 2)
+    assert "exists" in str(excinfo.value)
+
+
+@pytest.mark.parametrize("mode", ['w', 'w+'])
+def test_if_open_with_mode_w_truncates(file_stereo_rplus, mode):
+    with sf.SoundFile(file_stereo_rplus, mode, 48000, 6, format='AIFF') as f:
+        pass
+    with sf.SoundFile(filename_new) as f:
+        if isinstance(file_stereo_rplus, str):
+            assert f.samplerate == 48000
+            assert f.channels == 6
+            assert f.format == 'AIFF'
+            assert len(f) == 0
+        else:
+            # This doesn't really work for file descriptors and file objects
+            pass
 
 
 # -----------------------------------------------------------------------------