diff --git a/Lib/distutils/command/upload.py b/Lib/distutils/command/upload.py
--- a/Lib/distutils/command/upload.py
+++ b/Lib/distutils/command/upload.py
@@ -149,17 +149,17 @@ class upload(PyPIRCCommand):
         for key, value in data.items():
             title = '\nContent-Disposition: form-data; name="%s"' % key
             # handle multiple entries for the same name
             if type(value) != type([]):
                 value = [value]
             for value in value:
                 if type(value) is tuple:
                     title += '; filename="%s"' % value[0]
-                    value = value[1]
+                    value = str(value[1]).encode('utf-8')
                 else:
                     value = str(value).encode('utf-8')
                 body.write(sep_boundary)
                 body.write(title.encode('utf-8'))
                 body.write(b"\n\n")
                 body.write(value)
                 if value and value[-1:] == b'\r':
                     body.write(b'\n')  # write an extra newline (lurve Macs)