diff --git a/Lib/wave.py b/Lib/wave.py
index b5bb105..2877137 100644
--- a/Lib/wave.py
+++ b/Lib/wave.py
@@ -467,11 +467,11 @@
         self._datalength = self._nframes * self._nchannels * self._sampwidth
         self._form_length_pos = self._file.tell()
         self._file.write(struct.pack('<l4s4slhhllhh4s',
-            36 + self._datalength, 'WAVE', 'fmt ', 16,
+            36 + self._datalength, b'WAVE', b'fmt ', 16,
             WAVE_FORMAT_PCM, self._nchannels, self._framerate,
             self._nchannels * self._framerate * self._sampwidth,
             self._nchannels * self._sampwidth,
-            self._sampwidth * 8, 'data'))
+            self._sampwidth * 8, b'data'))
         self._data_length_pos = self._file.tell()
         self._file.write(struct.pack('<l', self._datalength))
         self._headerwritten = True