diff -r c092148a1b55 Lib/test/test_unicode.py
--- a/Lib/test/test_unicode.py	Tue Mar 01 10:26:10 2016 +0200
+++ b/Lib/test/test_unicode.py	Tue Mar 01 20:51:30 2016 +0100
@@ -347,6 +347,10 @@ class UnicodeTest(string_tests.CommonTes
                          "[a]")
         self.assertEqual("[\xe9]".translate(str.maketrans({'\xe9': None})),
                          "[]")
+        self.assertEqual('axb'.translate(str.maketrans({'a': None, 'b': '123'})),
+                         "x123")
+        self.assertEqual('axb'.translate(str.maketrans({'a': None, 'b': '\xe9'})),
+                         "x\xe9")
 
         # invalid Unicode characters
         invalid_char = 0x10ffff+1
diff -r c092148a1b55 Objects/unicodeobject.c
--- a/Objects/unicodeobject.c	Tue Mar 01 10:26:10 2016 +0200
+++ b/Objects/unicodeobject.c	Tue Mar 01 20:51:30 2016 +0100
@@ -8783,7 +8783,8 @@ unicode_fast_translate_lookup(PyObject *
    translated into writer, raise an exception and return -1 on error. */
 static int
 unicode_fast_translate(PyObject *input, PyObject *mapping,
-                       _PyUnicodeWriter *writer, int ignore)
+                       _PyUnicodeWriter *writer, int ignore,
+                       Py_ssize_t *input_pos)
 {
     Py_UCS1 ascii_table[128], ch, ch2;
     Py_ssize_t len;
@@ -8830,6 +8831,7 @@ unicode_fast_translate(PyObject *input, 
 
 exit:
     writer->pos = out - PyUnicode_1BYTE_DATA(writer->buffer);
+    *input_pos = in - PyUnicode_1BYTE_DATA(input);
     return res;
 }
 
@@ -8875,7 +8877,7 @@ static PyObject *
 
     ignore = (errors != NULL && strcmp(errors, "ignore") == 0);
 
-    res = unicode_fast_translate(input, mapping, &writer, ignore);
+    res = unicode_fast_translate(input, mapping, &writer, ignore, &i);
     if (res < 0) {
         _PyUnicodeWriter_Dealloc(&writer);
         return NULL;
@@ -8883,7 +8885,6 @@ static PyObject *
     if (res == 1)
         return _PyUnicodeWriter_Finish(&writer);
 
-    i = writer.pos;
     while (i<size) {
         /* try to encode it */
         int translate;