diff -r 07d8272d61e7 Lib/test/test_unicode.py
--- a/Lib/test/test_unicode.py	Mon Nov 28 12:06:13 2016 +0100
+++ b/Lib/test/test_unicode.py	Tue Nov 29 00:01:50 2016 +0800
@@ -2728,6 +2728,36 @@
             self.assertEqual(unicode_asucs4(s, len(s), 1), s+'\0')
             self.assertEqual(unicode_asucs4(s, len(s), 0), s+'\uffff')
 
+    # Test PyUnicode_FindChar()
+    @support.cpython_only
+    def test_findchar(self):
+        from _testcapi import unicode_findchar
+
+        str = "bye;\xe0 bient\xf4t;\u518d\u89c1;\U0001F44B" * 2
+
+        self.assertEqual(unicode_findchar(str, 'b', 0, len(str), 1), 0)
+        self.assertEqual(unicode_findchar(str, 'b', 0, len(str), -1), 24)
+        self.assertEqual(unicode_findchar(str, '\xe0', 0, len(str), 1), 4)
+        self.assertEqual(unicode_findchar(str, '\xe0', 0, len(str), -1), 22)
+        self.assertEqual(unicode_findchar(str, '\u518d', 0, len(str), 1), 14)
+        self.assertEqual(unicode_findchar(str, '\u518d', 0, len(str), -1), 32)
+        self.assertEqual(unicode_findchar(str, '\U0001F44B', 0, len(str), 1), 17)
+        self.assertEqual(unicode_findchar(str, '\U0001F44B', 0, len(str), -1), 35)
+
+        # start < end
+        self.assertEqual(unicode_findchar(str, 'b', 1, len(str), 1), 6)
+        self.assertEqual(unicode_findchar(str, 'b', 1, len(str)+1, 1), 6)
+        self.assertEqual(unicode_findchar(str, 'b', 1, 5, 1), -1)
+        # start > end
+        self.assertEqual(unicode_findchar(str, 'b', len(str), 0, 1), -1)
+        # start = end
+        self.assertEqual(unicode_findchar(str, 'b', 0, 0, 1), -1)
+        # negative
+        self.assertEqual(unicode_findchar(str, 'b', -len(str), len(str), 1), 0)
+        self.assertEqual(unicode_findchar(str, 'b', 0, -1, 1), 0)
+        self.assertEqual(unicode_findchar(str, 'b', -len(str), -1, 1), 0)
+        self.assertEqual(unicode_findchar(str, 'b', -1, -len(str), 1), -1)
+
     # Test PyUnicode_CopyCharacters()
     @support.cpython_only
     def test_copycharacters(self):
diff -r 07d8272d61e7 Modules/_testcapimodule.c
--- a/Modules/_testcapimodule.c	Mon Nov 28 12:06:13 2016 +0100
+++ b/Modules/_testcapimodule.c	Tue Nov 29 00:01:50 2016 +0800
@@ -1875,6 +1875,26 @@
 }
 
 static PyObject *
+unicode_findchar(PyObject *self, PyObject *args)
+{
+    PyObject *str;
+    int ch, direction;
+    Py_ssize_t result;
+    Py_ssize_t start, end;
+
+    if (!PyArg_ParseTuple(args, "UCnni:unicode_findchar", &str, &ch,
+                          &start, &end, &direction)) {
+        return NULL;
+    }
+
+    result = PyUnicode_FindChar(str, (Py_UCS4)ch, start, end, direction);
+    if (result == -2)
+        return NULL;
+    else
+        return PyLong_FromSsize_t(result);
+}
+
+static PyObject *
 unicode_copycharacters(PyObject *self, PyObject *args)
 {
     PyObject *from, *to, *to_copy;
@@ -4107,6 +4127,7 @@
     {"unicode_aswidechar",      unicode_aswidechar,              METH_VARARGS},
     {"unicode_aswidecharstring",unicode_aswidecharstring,        METH_VARARGS},
     {"unicode_asucs4",          unicode_asucs4,                  METH_VARARGS},
+    {"unicode_findchar",        unicode_findchar,                METH_VARARGS},
     {"unicode_copycharacters",  unicode_copycharacters,          METH_VARARGS},
     {"unicode_encodedecimal",   unicode_encodedecimal,           METH_VARARGS},
     {"unicode_transformdecimaltoascii", unicode_transformdecimaltoascii, METH_VARARGS},
diff -r 07d8272d61e7 Objects/unicodeobject.c
--- a/Objects/unicodeobject.c	Mon Nov 28 12:06:13 2016 +0100
+++ b/Objects/unicodeobject.c	Tue Nov 29 00:01:50 2016 +0800
@@ -9461,16 +9461,12 @@
                    int direction)
 {
     int kind;
-    Py_ssize_t result;
+    Py_ssize_t len, result;
     if (PyUnicode_READY(str) == -1)
         return -2;
-    if (start < 0 || end < 0) {
-        PyErr_SetString(PyExc_IndexError, "string index out of range");
-        return -2;
-    }
-    if (end > PyUnicode_GET_LENGTH(str))
-        end = PyUnicode_GET_LENGTH(str);
-    if (start >= end)
+    len = PyUnicode_GET_LENGTH(str);
+    ADJUST_INDICES(start, end, len);
+    if (end - start < 1)
         return -1;
     kind = PyUnicode_KIND(str);
     result = findchar(PyUnicode_1BYTE_DATA(str) + kind*start,