diff --git a/Lib/email/encoders.py b/Lib/email/encoders.py
index 20feb02..0ea441d 100644
--- a/Lib/email/encoders.py
+++ b/Lib/email/encoders.py
@@ -29,7 +29,7 @@
     Also, add an appropriate Content-Transfer-Encoding header.
     """
     orig = msg.get_payload()
-    encdata = _bencode(orig)
+    encdata = str(_bencode(orig), 'ascii')
     msg.set_payload(encdata)
     msg['Content-Transfer-Encoding'] = 'base64'
 
diff --git a/Lib/email/test/test_email.py b/Lib/email/test/test_email.py
index 44a47c5..79146a3 100644
--- a/Lib/email/test/test_email.py
+++ b/Lib/email/test/test_email.py
@@ -970,7 +970,8 @@
 
     def test_encoding(self):
         payload = self._au.get_payload()
-        self.assertEqual(base64.decodebytes(payload), self._audiodata)
+        self.assertEqual(base64.decodebytes(bytes(payload, 'ascii')),
+                self._audiodata)
 
     def test_checkSetMinor(self):
         au = MIMEAudio(self._audiodata, 'fish')
@@ -1010,7 +1011,8 @@
 
     def test_encoding(self):
         payload = self._im.get_payload()
-        self.assertEqual(base64.decodebytes(payload), self._imgdata)
+        self.assertEqual(base64.decodebytes(bytes(payload, 'ascii')),
+                self._imgdata)
 
     def test_checkSetMinor(self):
         im = MIMEImage(self._imgdata, 'fish')
@@ -1050,7 +1052,7 @@
         eq = self.assertEqual
         bytes = b'\xfa\xfb\xfc\xfd\xfe\xff'
         msg = MIMEApplication(bytes)
-        eq(msg.get_payload(), b'+vv8/f7/')
+        eq(msg.get_payload(), '+vv8/f7/')
         eq(msg.get_payload(decode=True), bytes)
 
 
diff --git a/Misc/ACKS b/Misc/ACKS
index b75ff6c..2fb8b5b 100644
--- a/Misc/ACKS
+++ b/Misc/ACKS
@@ -83,6 +83,7 @@
 Paul Boddie
 Matthew Boedicker
 David Bolen
+Forest Bond
 Gawain Bolton
 Gregory Bond
 Jurjen Bos
diff --git a/Misc/NEWS b/Misc/NEWS
index 9195a04..0dff231 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -398,6 +398,9 @@
 Library
 -------
 
+- Issue #4768: base64 encoded email body parts were incorrectly stored as
+  binary strings.  They are now correctly converted to strings.
+
 - Issue #8833: tarfile created hard link entries with a size field != 0 by
   mistake.