diff --git a/src/calibre/devices/mtp/unix/driver.py b/src/calibre/devices/mtp/unix/driver.py
index e023ac00d2..17284dd259 100644
--- a/src/calibre/devices/mtp/unix/driver.py
+++ b/src/calibre/devices/mtp/unix/driver.py
@@ -12,8 +12,8 @@ from threading import RLock
 from collections import namedtuple
 from functools import partial
 
-from calibre import prints, as_unicode
-from calibre.constants import plugins, islinux, isosx
+from calibre import prints, as_unicode, force_unicode
+from calibre.constants import plugins, islinux, isosx, ispy3
 from calibre.ptempfile import SpooledTemporaryFile
 from calibre.devices.errors import OpenFailed, DeviceError, BlacklistedDevice, OpenActionNeeded
 from calibre.devices.mtp.base import MTPDeviceBase, synchronous, debug
@@ -166,8 +166,12 @@ class MTP_DEVICE(MTPDeviceBase):
     @synchronous
     def create_device(self, connected_device):
         d = connected_device
+        man, prod = d.manufacturer, d.prod
+        if ispy3:
+            man = force_unicode(man, 'utf-8') if isinstance(man, bytes) else man
+            prod = force_unicode(prod, 'utf-8') if isinstance(prod, bytes) else prod
         return self.libmtp.Device(d.busnum, d.devnum, d.vendor_id,
-                d.product_id, d.manufacturer, d.product, d.serial)
+                d.product_id, man, prod, d.serial)
 
     @synchronous
     def eject(self):
diff --git a/src/calibre/utils/podofo/doc.cpp b/src/calibre/utils/podofo/doc.cpp
index 9f19b47446..164bc17cb7 100644
--- a/src/calibre/utils/podofo/doc.cpp
+++ b/src/calibre/utils/podofo/doc.cpp
@@ -83,7 +83,7 @@ static PyObject *
 PDFDoc_save(PDFDoc *self, PyObject *args) {
     char *buffer;
 
-    if (PyArg_ParseTuple(args, BYTES_FMT, &buffer)) {
+    if (PyArg_ParseTuple(args, "s", &buffer)) {
         try {
             self->doc->Write(buffer);
         } catch(const PdfError & err) {