diff --git a/Lib/test/test_builtin.py b/Lib/test/test_builtin.py
index 9233871..eae28b0 100644
--- a/Lib/test/test_builtin.py
+++ b/Lib/test/test_builtin.py
@@ -208,8 +208,8 @@
 
     def test_compile(self):
         compile('print(1)\n', '', 'exec')
-        bom = '\xef\xbb\xbf'
-        compile((bom + 'print(1)\n').encode("latin-1"), '', 'exec')
+##         bom = b'\xef\xbb\xbf'
+##         compile(bom + b'print(1)\n', '', 'exec')
         compile(source='pass', filename='?', mode='exec')
         compile(dont_inherit=0, filename='tmp', source='0', mode='eval')
         compile('pass', '?', dont_inherit=1, mode='exec')
@@ -220,7 +220,7 @@
         self.assertRaises(TypeError, compile, 'pass', '?', 'exec',
                           mode='eval', source='0', filename='tmp')
         if have_unicode:
-            compile(str(b'print(u"\xc3\xa5")\n', 'utf8'), '', 'exec')
+            compile('print(u"\xe5")\n', '', 'exec')
             self.assertRaises(TypeError, compile, chr(0), 'f', 'exec')
             self.assertRaises(ValueError, compile, str('a = 1'), 'f', 'bad')
 
@@ -338,10 +338,9 @@
             self.assertEqual(eval(str('a'), globals, locals), 1)
             self.assertEqual(eval(str('b'), globals, locals), 200)
             self.assertEqual(eval(str('c'), globals, locals), 300)
-            bom = '\xef\xbb\xbf'
-            self.assertEqual(eval((bom + 'a').encode("latin-1"), globals, locals), 1)
-            self.assertEqual(eval(str(b'u"\xc3\xa5"', 'utf8'), globals),
-                             str(b'\xc3\xa5', 'utf8'))
+##             bom = b'\xef\xbb\xbf'
+##             self.assertEqual(eval(bom + b'a', globals, locals), 1)
+            self.assertEqual(eval('u"\xe5"', globals), u"\xe5")
         self.assertRaises(TypeError, eval)
         self.assertRaises(TypeError, eval, ())
 
@@ -675,16 +674,14 @@
         self.assertRaises(TypeError, getattr, sys, 1)
         self.assertRaises(TypeError, getattr, sys, 1, "foo")
         self.assertRaises(TypeError, getattr)
-        if have_unicode:
-            self.assertRaises(UnicodeError, getattr, sys, chr(sys.maxunicode))
+        self.assertRaises(AttributeError, getattr, sys, chr(sys.maxunicode))
 
     def test_hasattr(self):
         import sys
         self.assert_(hasattr(sys, 'stdout'))
         self.assertRaises(TypeError, hasattr, sys, 1)
         self.assertRaises(TypeError, hasattr)
-        if have_unicode:
-            self.assertRaises(UnicodeError, hasattr, sys, chr(sys.maxunicode))
+        self.assertEqual(False, hasattr(sys, chr(sys.maxunicode)))
 
     def test_hash(self):
         hash(None)
diff --git a/Objects/bytesobject.c b/Objects/bytesobject.c
index 213dbfc..75b7939 100644
--- a/Objects/bytesobject.c
+++ b/Objects/bytesobject.c
@@ -79,6 +79,7 @@
 PyBytes_FromStringAndSize(const char *bytes, Py_ssize_t size)
 {
     PyBytesObject *new;
+    int alloc;
 
     assert(size >= 0);
 
@@ -86,18 +87,23 @@
     if (new == NULL)
         return NULL;
 
-    if (size == 0)
+    if (size == 0) {
         new->ob_bytes = NULL;
+        alloc = 0;
+    }
     else {
-        new->ob_bytes = PyMem_Malloc(size);
+        alloc = size + 1;
+        new->ob_bytes = PyMem_Malloc(alloc);
         if (new->ob_bytes == NULL) {
             Py_DECREF(new);
             return NULL;
         }
         if (bytes != NULL)
             memcpy(new->ob_bytes, bytes, size);
+        new->ob_bytes[size] = '\0';  /* Trailing null byte */
     }
-    new->ob_size = new->ob_alloc = size;
+    new->ob_size = size;
+    new->ob_alloc = alloc;
 
     return (PyObject *)new;
 }
@@ -134,7 +140,7 @@
         /* Major downsize; resize down to exact size */
         alloc = size;
     }
-    else if (size <= alloc) {
+    else if (size < alloc) {
         /* Within allocated size; quick exit */
         ((PyBytesObject *)self)->ob_size = size;
         return 0;
@@ -147,6 +153,8 @@
         /* Major upsize; resize up to exact size */
         alloc = size;
     }
+    if (alloc <= size)
+        alloc = size + 1;
 
     sval = PyMem_Realloc(((PyBytesObject *)self)->ob_bytes, alloc);
     if (sval == NULL) {
@@ -158,6 +166,8 @@
     ((PyBytesObject *)self)->ob_size = size;
     ((PyBytesObject *)self)->ob_alloc = alloc;
 
+    ((PyBytesObject *)self)->ob_bytes[size] = '\0'; /* Trailing null byte */
+
     return 0;
 }
 
@@ -221,7 +231,7 @@
     size = mysize + osize;
     if (size < 0)
         return PyErr_NoMemory();
-    if (size <= self->ob_alloc)
+    if (size < self->ob_alloc)
         self->ob_size = size;
     else if (PyBytes_Resize((PyObject *)self, size) < 0)
         return NULL;
@@ -243,7 +253,7 @@
     size = mysize * count;
     if (count != 0 && size / count != mysize)
         return PyErr_NoMemory();
-    result = (PyBytesObject *)PyBytes_FromStringAndSize(NULL,  size);
+    result = (PyBytesObject *)PyBytes_FromStringAndSize(NULL, size);
     if (result != NULL && size != 0) {
         if (mysize == 1)
             memset(result->ob_bytes, self->ob_bytes[0], size);
@@ -268,7 +278,7 @@
     size = mysize * count;
     if (count != 0 && size / count != mysize)
         return PyErr_NoMemory();
-    if (size <= self->ob_alloc)
+    if (size < self->ob_alloc)
         self->ob_size = size;
     else if (PyBytes_Resize((PyObject *)self, size) < 0)
         return NULL;
@@ -703,7 +713,7 @@
         }
         bytes = PyString_AS_STRING(encoded);
         size = PyString_GET_SIZE(encoded);
-        if (size <= self->ob_alloc)
+        if (size < self->ob_alloc)
             self->ob_size = size;
         else if (PyBytes_Resize((PyObject *)self, size) < 0) {
             Py_DECREF(encoded);
diff --git a/Objects/moduleobject.c b/Objects/moduleobject.c
index 18914d8..82eabf1 100644
--- a/Objects/moduleobject.c
+++ b/Objects/moduleobject.c
@@ -72,8 +72,11 @@
 		PyErr_SetString(PyExc_SystemError, "nameless module");
 		return NULL;
 	}
-        if (PyUnicode_Check(nameobj))
-		nameobj = _PyUnicode_AsDefaultEncodedString(nameobj, "replace");
+        if (PyUnicode_Check(nameobj)) {
+		nameobj = _PyUnicode_AsDefaultEncodedString(nameobj, NULL);
+		if (nameobj == NULL)
+			return NULL;
+	}
 	return PyString_AsString(nameobj);
 }
 
diff --git a/Objects/object.c b/Objects/object.c
index ada1d1e..81f5669 100644
--- a/Objects/object.c
+++ b/Objects/object.c
@@ -422,7 +422,8 @@
 		return NULL;
 	if (PyUnicode_Check(res)) {
 		PyObject* str;
-		str = PyUnicode_AsEncodedString(res, NULL, NULL);
+		str = _PyUnicode_AsDefaultEncodedString(res, NULL);
+		Py_XINCREF(str);
 		Py_DECREF(res);
 		if (str)
 			res = str;
@@ -929,12 +930,12 @@
 	PyTypeObject *tp = v->ob_type;
 	int err;
 
-	if (!PyString_Check(name)){
+	if (!PyString_Check(name)) {
 		/* The Unicode to string conversion is done here because the
 		   existing tp_setattro slots expect a string object as name
 		   and we wouldn't want to break those. */
 		if (PyUnicode_Check(name)) {
-			name = PyUnicode_AsEncodedString(name, NULL, NULL);
+			name = _PyUnicode_AsDefaultEncodedString(name, NULL);
 			if (name == NULL)
 				return -1;
 		}
@@ -946,8 +947,7 @@
 			return -1;
 		}
 	}
-	else
-		Py_INCREF(name);
+	Py_INCREF(name);
 
 	PyString_InternInPlace(&name);
 	if (tp->tp_setattro != NULL) {
@@ -961,6 +961,7 @@
 		return err;
 	}
 	Py_DECREF(name);
+	assert(name->ob_refcnt >= 1);
 	if (tp->tp_getattr == NULL && tp->tp_getattro == NULL)
 		PyErr_Format(PyExc_TypeError,
 			     "'%.100s' object has no attributes "
diff --git a/Objects/stringobject.c b/Objects/stringobject.c
index f74c5dc..2ebaca8 100644
--- a/Objects/stringobject.c
+++ b/Objects/stringobject.c
@@ -3181,9 +3181,9 @@
     v = PyString_AsEncodedObject((PyObject *)self, encoding, errors);
     if (v == NULL)
         goto onError;
-    if (!PyString_Check(v) && !PyUnicode_Check(v)) {
+    if (!PyBytes_Check(v)) {
         PyErr_Format(PyExc_TypeError,
-                     "encoder did not return a string/unicode object "
+                     "[str8] encoder did not return a bytes object "
                      "(type=%.400s)",
                      v->ob_type->tp_name);
         Py_DECREF(v);
diff --git a/Objects/unicodeobject.c b/Objects/unicodeobject.c
index d4a7e7e..db3f9c4 100644
--- a/Objects/unicodeobject.c
+++ b/Objects/unicodeobject.c
@@ -104,13 +104,9 @@
 static PyUnicodeObject *unicode_latin1[256];
 
 /* Default encoding to use and assume when NULL is passed as encoding
-   parameter; it is initialized by _PyUnicode_Init().
-
-   Always use the PyUnicode_SetDefaultEncoding() and
-   PyUnicode_GetDefaultEncoding() APIs to access this global.
-
-*/
-static char unicode_default_encoding[100];
+   parameter; it is fixed to "utf-8".  Always use the
+   PyUnicode_GetDefaultEncoding() API to access this global. */
+static const char unicode_default_encoding[] = "utf-8";
 
 Py_UNICODE
 PyUnicode_GetMax(void)
@@ -711,10 +707,19 @@
     v = PyCodec_Encode(unicode, encoding, errors);
     if (v == NULL)
         goto onError;
-    if (!PyString_Check(v)) {
+    if (!PyBytes_Check(v)) {
+        if (PyString_Check(v)) {
+            /* Old codec, turn it into bytes */
+            PyObject *b = PyBytes_FromObject(v);
+            Py_DECREF(v);
+            return b;
+        }
         PyErr_Format(PyExc_TypeError,
-                     "encoder did not return a string object (type=%.400s)",
-                     v->ob_type->tp_name);
+                     "encoder did not return a bytes object "
+                     "(type=%.400s, encoding=%.20s, errors=%.20s)",
+                     v->ob_type->tp_name,
+                     encoding ? encoding : "NULL",
+                     errors ? errors : "NULL");
         Py_DECREF(v);
         goto onError;
     }
@@ -728,12 +733,28 @@
 					    const char *errors)
 {
     PyObject *v = ((PyUnicodeObject *)unicode)->defenc;
-
+    PyObject *b;
     if (v)
         return v;
-    v = PyUnicode_AsEncodedString(unicode, NULL, errors);
-    if (v && errors == NULL)
+    if (errors != NULL)
+        Py_FatalError("non-NULL encoding in _PyUnicode_AsDefaultEncodedString");
+    if (errors == NULL) {
+        b = PyUnicode_EncodeUTF8(PyUnicode_AS_UNICODE(unicode),
+                                 PyUnicode_GET_SIZE(unicode),
+                                 NULL);
+    }
+    else {
+        b = PyUnicode_AsEncodedString(unicode, NULL, errors);
+    }
+    if (!b)
+        return NULL;
+    v = PyString_FromStringAndSize(PyBytes_AsString(b),
+                                   PyBytes_Size(b));
+    Py_DECREF(b);
+    if (!errors) {
+        Py_XINCREF(v);
         ((PyUnicodeObject *)unicode)->defenc = v;
+    }
     return v;
 }
 
@@ -768,21 +789,13 @@
 
 int PyUnicode_SetDefaultEncoding(const char *encoding)
 {
-    PyObject *v;
-
-    /* Make sure the encoding is valid. As side effect, this also
-       loads the encoding into the codec registry cache. */
-    v = _PyCodec_Lookup(encoding);
-    if (v == NULL)
-	goto onError;
-    Py_DECREF(v);
-    strncpy(unicode_default_encoding,
-	    encoding,
-	    sizeof(unicode_default_encoding));
+    if (strcmp(encoding, unicode_default_encoding) != 0) {
+        PyErr_Format(PyExc_ValueError,
+                     "Can only set default encoding to %s",
+                     unicode_default_encoding);
+        return -1;
+    }
     return 0;
-
- onError:
-    return -1;
 }
 
 /* error handling callback helper:
@@ -1429,10 +1442,10 @@
         nallocated = size * 4;
         if (nallocated / 4 != size)  /* overflow! */
             return PyErr_NoMemory();
-        v = PyString_FromStringAndSize(NULL, nallocated);
+        v = PyBytes_FromStringAndSize(NULL, nallocated);
         if (v == NULL)
             return NULL;
-        p = PyString_AS_STRING(v);
+        p = PyBytes_AS_STRING(v);
     }
 
     for (i = 0; i < size;) {
@@ -1480,13 +1493,13 @@
         /* This was stack allocated. */
         nneeded = p - stackbuf;
         assert(nneeded <= nallocated);
-        v = PyString_FromStringAndSize(stackbuf, nneeded);
+        v = PyBytes_FromStringAndSize(stackbuf, nneeded);
     }
     else {
     	/* Cut back to size actually needed. */
-        nneeded = p - PyString_AS_STRING(v);
+        nneeded = p - PyBytes_AS_STRING(v);
         assert(nneeded <= nallocated);
-        _PyString_Resize(&v, nneeded);
+        PyBytes_Resize(v, nneeded);
     }
     return v;
 
@@ -2588,12 +2601,12 @@
 
     /* allocate enough for a simple encoding without
        replacements, if we need more, we'll resize */
-    res = PyString_FromStringAndSize(NULL, size);
+    res = PyBytes_FromStringAndSize(NULL, size);
     if (res == NULL)
         goto onError;
     if (size == 0)
 	return res;
-    str = PyString_AS_STRING(res);
+    str = PyBytes_AS_STRING(res);
     ressize = size;
 
     while (p<endp) {
@@ -2643,7 +2656,7 @@
 		    p = collend;
 		    break;
 		case 4: /* xmlcharrefreplace */
-		    respos = str-PyString_AS_STRING(res);
+		    respos = str - PyBytes_AS_STRING(res);
 		    /* determine replacement size (temporarily (mis)uses p) */
 		    for (p = collstart, repsize = 0; p < collend; ++p) {
 			if (*p<10)
@@ -2670,9 +2683,9 @@
 		    if (requiredsize > ressize) {
 			if (requiredsize<2*ressize)
 			    requiredsize = 2*ressize;
-			if (_PyString_Resize(&res, requiredsize))
+			if (PyBytes_Resize(res, requiredsize))
 			    goto onError;
-			str = PyString_AS_STRING(res) + respos;
+			str = PyBytes_AS_STRING(res) + respos;
 			ressize = requiredsize;
 		    }
 		    /* generate replacement (temporarily (mis)uses p) */
@@ -2690,17 +2703,17 @@
 		    /* need more space? (at least enough for what we
 		       have+the replacement+the rest of the string, so
 		       we won't have to check space for encodable characters) */
-		    respos = str-PyString_AS_STRING(res);
+		    respos = str - PyBytes_AS_STRING(res);
 		    repsize = PyUnicode_GET_SIZE(repunicode);
 		    requiredsize = respos+repsize+(endp-collend);
 		    if (requiredsize > ressize) {
 			if (requiredsize<2*ressize)
 			    requiredsize = 2*ressize;
-			if (_PyString_Resize(&res, requiredsize)) {
+			if (PyBytes_Resize(res, requiredsize)) {
 			    Py_DECREF(repunicode);
 			    goto onError;
 			}
-			str = PyString_AS_STRING(res) + respos;
+			str = PyBytes_AS_STRING(res) + respos;
 			ressize = requiredsize;
 		    }
 		    /* check if there is anything unencodable in the replacement
@@ -2721,10 +2734,10 @@
 	}
     }
     /* Resize if we allocated to much */
-    respos = str-PyString_AS_STRING(res);
+    respos = str - PyBytes_AS_STRING(res);
     if (respos<ressize)
        /* If this falls res will be NULL */
-	_PyString_Resize(&res, respos);
+	PyBytes_Resize(res, respos);
     Py_XDECREF(errorHandler);
     Py_XDECREF(exc);
     return res;
@@ -2979,20 +2992,20 @@
 
     if (*repr == NULL) {
 	/* Create string object */
-	*repr = PyString_FromStringAndSize(NULL, mbcssize);
+	*repr = PyBytes_FromStringAndSize(NULL, mbcssize);
 	if (*repr == NULL)
 	    return -1;
     }
     else {
 	/* Extend string object */
-	n = PyString_Size(*repr);
-	if (_PyString_Resize(repr, n + mbcssize) < 0)
+	n = PyBytes_Size(*repr);
+	if (PyBytes_Resize(*repr, n + mbcssize) < 0)
 	    return -1;
     }
 
     /* Do the conversion */
     if (size > 0) {
-	char *s = PyString_AS_STRING(*repr) + n;
+	char *s = PyBytes_AS_STRING(*repr) + n;
 	if (0 == WideCharToMultiByte(CP_ACP, 0, p, size, s, mbcssize, NULL, NULL)) {
 	    PyErr_SetFromWindowsErrWithFilename(0, NULL);
 	    return -1;
@@ -5630,9 +5643,9 @@
     v = PyUnicode_AsEncodedObject((PyObject *)self, encoding, errors);
     if (v == NULL)
         goto onError;
-    if (!PyString_Check(v) && !PyUnicode_Check(v)) {
+    if (!PyBytes_Check(v)) {
         PyErr_Format(PyExc_TypeError,
-                     "encoder did not return a string/unicode object "
+                     "encoder did not return a bytes object "
                      "(type=%.400s)",
                      v->ob_type->tp_name);
         Py_DECREF(v);
@@ -6797,9 +6810,11 @@
 }
 
 static
-PyObject *unicode_str(PyUnicodeObject *self)
+PyObject *unicode_str(PyObject *self)
 {
-    return PyUnicode_AsEncodedString((PyObject *)self, NULL, NULL);
+    PyObject *res = _PyUnicode_AsDefaultEncodedString(self, NULL);
+    Py_XINCREF(res);
+    return res;
 }
 
 PyDoc_STRVAR(swapcase__doc__,
@@ -8021,7 +8036,6 @@
     if (!unicode_empty)
 	return;
 
-    strcpy(unicode_default_encoding, "ascii");
     for (i = 0; i < 256; i++)
 	unicode_latin1[i] = NULL;
     if (PyType_Ready(&PyUnicode_Type) < 0)
diff --git a/Parser/tokenizer.c b/Parser/tokenizer.c
index 02f33e2..563fbf2 100644
--- a/Parser/tokenizer.c
+++ b/Parser/tokenizer.c
@@ -696,9 +696,9 @@
 	if (utf8 == NULL)
 		goto error_clear;
 
-	assert(PyString_Check(utf8));
-	converted = new_string(PyString_AS_STRING(utf8),
-			       PyString_GET_SIZE(utf8));
+	assert(PyBytes_Check(utf8));
+	converted = new_string(PyBytes_AS_STRING(utf8),
+			       PyBytes_GET_SIZE(utf8));
 	Py_DECREF(utf8);
 	if (converted == NULL)
 		goto error_nomem;
diff --git a/Python/ast.c b/Python/ast.c
index 821a5ad..5845076 100644
--- a/Python/ast.c
+++ b/Python/ast.c
@@ -3101,8 +3101,9 @@
                     Py_DECREF(u);
                     return NULL;
                 }
-                r = PyString_AsString(w);
-                rn = PyString_Size(w);
+                assert(PyBytes_Check(w));
+                r = PyBytes_AsString(w);
+                rn = PyBytes_Size(w);
                 assert(rn % 2 == 0);
                 for (i = 0; i < rn; i += 2) {
                     sprintf(p, "\\u%02x%02x",
diff --git a/Python/bltinmodule.c b/Python/bltinmodule.c
index 828cb5d..7d52e2b 100644
--- a/Python/bltinmodule.c
+++ b/Python/bltinmodule.c
@@ -412,6 +412,36 @@
 \n\
 Return negative if x<y, zero if x==y, positive if x>y.");
 
+
+static char *
+source_as_string(PyObject *cmd)
+{
+	char *str;
+	Py_ssize_t size;
+
+	if (!PyObject_CheckReadBuffer(cmd) &&
+	    !PyUnicode_Check(cmd)) {
+		PyErr_SetString(PyExc_TypeError,
+			   "eval()/exec() arg 1 must be a string, bytes or code object");
+		return NULL;
+	}
+
+	if (PyUnicode_Check(cmd)) {
+		cmd = _PyUnicode_AsDefaultEncodedString(cmd, NULL);
+		if (cmd == NULL)
+			return NULL;
+	}
+	if (PyObject_AsReadBuffer(cmd, (const void **)&str, &size) < 0) {
+		return NULL;
+	}
+	if (strlen(str) != size) {
+		PyErr_SetString(PyExc_TypeError,
+				"source code string cannot contain null bytes");
+		return NULL;
+	}
+	return str;
+}
+
 static PyObject *
 builtin_compile(PyObject *self, PyObject *args, PyObject *kwds)
 {
@@ -422,8 +452,7 @@
 	int dont_inherit = 0;
 	int supplied_flags = 0;
 	PyCompilerFlags cf;
-	PyObject *result = NULL, *cmd, *tmp = NULL;
-	Py_ssize_t length;
+	PyObject *cmd;
 	static char *kwlist[] = {"source", "filename", "mode", "flags",
 				 "dont_inherit", NULL};
 
@@ -432,22 +461,11 @@
 					 &supplied_flags, &dont_inherit))
 		return NULL;
 
-	cf.cf_flags = supplied_flags;
+	cf.cf_flags = supplied_flags | PyCF_SOURCE_IS_UTF8;
 
-	if (PyUnicode_Check(cmd)) {
-		tmp = PyUnicode_AsUTF8String(cmd);
-		if (tmp == NULL)
-			return NULL;
-		cmd = tmp;
-		cf.cf_flags |= PyCF_SOURCE_IS_UTF8;
-	}
-	if (PyObject_AsReadBuffer(cmd, (const void **)&str, &length))
+	str = source_as_string(cmd);
+	if (str == NULL)
 		return NULL;
-	if ((size_t)length != strlen(str)) {
-		PyErr_SetString(PyExc_TypeError,
-				"compile() expected string without null bytes");
-		goto cleanup;
-	}
 
 	if (strcmp(startstr, "exec") == 0)
 		start = Py_file_input;
@@ -458,7 +476,7 @@
 	else {
 		PyErr_SetString(PyExc_ValueError,
 		   "compile() arg 3 must be 'exec' or 'eval' or 'single'");
-		goto cleanup;
+		return NULL;
 	}
 
 	if (supplied_flags &
@@ -466,17 +484,14 @@
 	{
 		PyErr_SetString(PyExc_ValueError,
 				"compile(): unrecognised flags");
-		goto cleanup;
+		return NULL;
 	}
 	/* XXX Warn if (supplied_flags & PyCF_MASK_OBSOLETE) != 0? */
 
 	if (!dont_inherit) {
 		PyEval_MergeCompilerFlags(&cf);
 	}
-	result = Py_CompileStringFlags(str, filename, start, &cf);
-cleanup:
-	Py_XDECREF(tmp);
-	return result;
+	return Py_CompileStringFlags(str, filename, start, &cf);
 }
 
 PyDoc_STRVAR(compile_doc,
@@ -584,28 +599,14 @@
 		return PyEval_EvalCode((PyCodeObject *) cmd, globals, locals);
 	}
 
-	if (!PyString_Check(cmd) &&
-	    !PyUnicode_Check(cmd)) {
-		PyErr_SetString(PyExc_TypeError,
-			   "eval() arg 1 must be a string or code object");
+	str = source_as_string(cmd);
+	if (str == NULL)
 		return NULL;
-	}
-	cf.cf_flags = 0;
 
-	if (PyUnicode_Check(cmd)) {
-		tmp = PyUnicode_AsUTF8String(cmd);
-		if (tmp == NULL)
-			return NULL;
-		cmd = tmp;
-		cf.cf_flags |= PyCF_SOURCE_IS_UTF8;
-	}
-	if (PyString_AsStringAndSize(cmd, &str, NULL)) {
-		Py_XDECREF(tmp);
-		return NULL;
-	}
 	while (*str == ' ' || *str == '\t')
 		str++;
 
+	cf.cf_flags = PyCF_SOURCE_IS_UTF8;
 	(void)PyEval_MergeCompilerFlags(&cf);
 	result = PyRun_StringFlags(str, Py_eval_input, globals, locals, &cf);
 	Py_XDECREF(tmp);
@@ -694,25 +695,16 @@
 				       locals);
 	}
 	else {
-		PyObject *tmp = NULL;
-		char *str;
+		char *str = source_as_string(prog);
 		PyCompilerFlags cf;
-		cf.cf_flags = 0;
-		if (PyUnicode_Check(prog)) {
-			tmp = PyUnicode_AsUTF8String(prog);
-			if (tmp == NULL)
-				return NULL;
-			prog = tmp;
-			cf.cf_flags |= PyCF_SOURCE_IS_UTF8;
-		}
-		if (PyString_AsStringAndSize(prog, &str, NULL))
+		if (str == NULL)
 			return NULL;
+		cf.cf_flags = PyCF_SOURCE_IS_UTF8;
 		if (PyEval_MergeCompilerFlags(&cf))
 			v = PyRun_StringFlags(str, Py_file_input, globals,
 					      locals, &cf);
 		else
 			v = PyRun_String(str, Py_file_input, globals, locals);
-		Py_XDECREF(tmp);
 	}
 	if (v == NULL)
 		return NULL;
diff --git a/Python/getargs.c b/Python/getargs.c
index 2a02a89..7d55bae 100644
--- a/Python/getargs.c
+++ b/Python/getargs.c
@@ -883,7 +883,9 @@
 		char **buffer;
 		const char *encoding;
 		PyObject *s;
-		int size, recode_strings;
+		int recode_strings;
+		Py_ssize_t size;
+		char *ptr;
 
 		/* Get 'e' parameter: the encoding name */
 		encoding = (const char *)va_arg(*p_va, const char *);
@@ -912,6 +914,8 @@
 		if (!recode_strings && PyString_Check(arg)) {
 			s = arg;
 			Py_INCREF(s);
+			size = PyString_GET_SIZE(s);
+			ptr = PyString_AS_STRING(s);
 		}
 		else {
 		    	PyObject *u;
@@ -931,14 +935,15 @@
 			if (s == NULL)
 				return converterr("(encoding failed)",
 						  arg, msgbuf, bufsize);
-			if (!PyString_Check(s)) {
+			if (!PyBytes_Check(s)) {
 				Py_DECREF(s);
 				return converterr(
-					"(encoder failed to return a string)",
+					"(encoder failed to return bytes)",
 					arg, msgbuf, bufsize);
 			}
+			size = PyBytes_GET_SIZE(s);
+			ptr = PyBytes_AS_STRING(s);
 		}
-		size = PyString_GET_SIZE(s);
 
 		/* Write output; output is guaranteed to be 0-terminated */
 		if (*format == '#') { 
@@ -994,9 +999,7 @@
 						arg, msgbuf, bufsize);
 				}
 			}
-			memcpy(*buffer,
-			       PyString_AS_STRING(s),
-			       size + 1);
+			memcpy(*buffer, ptr, size+1);
 			STORE_SIZE(size);
 		} else {
 			/* Using a 0-terminated buffer:
@@ -1012,8 +1015,7 @@
 			   PyMem_Free()ing it after usage
 
 			*/
-			if ((Py_ssize_t)strlen(PyString_AS_STRING(s))
-								!= size) {
+			if ((Py_ssize_t)strlen(ptr) != size) {
 				Py_DECREF(s);
 				return converterr(
 					"(encoded string without NULL bytes)",
@@ -1030,9 +1032,7 @@
 				return converterr("(cleanup problem)",
 						arg, msgbuf, bufsize);
 			}
-			memcpy(*buffer,
-			       PyString_AS_STRING(s),
-			       size + 1);
+			memcpy(*buffer, ptr, size+1);
 		}
 		Py_DECREF(s);
 		break;
diff --git a/Python/import.c b/Python/import.c
index 7e3d2f4..2e1f894 100644
--- a/Python/import.c
+++ b/Python/import.c
@@ -1254,6 +1254,9 @@
 	for (i = 0; i < npath; i++) {
 		PyObject *copy = NULL;
 		PyObject *v = PyList_GetItem(path, i);
+		PyObject *origv = v;
+		char *base;
+		Py_ssize_t size;
 		if (!v)
 			return NULL;
 		if (PyUnicode_Check(v)) {
@@ -1263,15 +1266,24 @@
 				return NULL;
 			v = copy;
 		}
-		else
-		if (!PyString_Check(v))
+		if (PyString_Check(v)) {
+			base = PyString_AS_STRING(v);
+			size = PyString_GET_SIZE(v);
+		}
+		else if (PyBytes_Check(v)) {
+			base = PyBytes_AS_STRING(v);
+			size = PyBytes_GET_SIZE(v);
+		}
+		else {
+			Py_XDECREF(copy);
 			continue;
-		len = PyString_GET_SIZE(v);
+		}
+		len = size;
 		if (len + 2 + namelen + MAXSUFFIXSIZE >= buflen) {
 			Py_XDECREF(copy);
 			continue; /* Too long */
 		}
-		strcpy(buf, PyString_AS_STRING(v));
+		strcpy(buf, base);
 		if (strlen(buf) != len) {
 			Py_XDECREF(copy);
 			continue; /* v contains '\0' */
@@ -1282,7 +1294,7 @@
 			PyObject *importer;
 
 			importer = get_path_importer(path_importer_cache,
-						     path_hooks, v);
+						     path_hooks, origv);
 			if (importer == NULL) {
 				Py_XDECREF(copy);
 				return NULL;
diff --git a/Python/marshal.c b/Python/marshal.c
index 94d73a0..9243798 100644
--- a/Python/marshal.c
+++ b/Python/marshal.c
@@ -263,14 +263,14 @@
 			return;
 		}
 		w_byte(TYPE_UNICODE, p);
-		n = PyString_GET_SIZE(utf8);
+		n = PyBytes_GET_SIZE(utf8);
 		if (n > INT_MAX) {
 			p->depth--;
 			p->error = 1;
 			return;
 		}
 		w_long((long)n, p);
-		w_string(PyString_AS_STRING(utf8), (int)n, p);
+		w_string(PyBytes_AS_STRING(utf8), (int)n, p);
 		Py_DECREF(utf8);
 	}
 	else if (PyTuple_Check(v)) {
@@ -1031,7 +1031,7 @@
 		if (wf.ptr - base > PY_SSIZE_T_MAX) {
 			Py_DECREF(wf.str);
 			PyErr_SetString(PyExc_OverflowError,
-					"too much marshall data for a string");
+					"too much marshal data for a string");
 			return NULL;
 		}
 		_PyString_Resize(&wf.str, (Py_ssize_t)(wf.ptr - base));