diff -r 10a73648c92c Doc/library/sqlite3.rst
--- a/Doc/library/sqlite3.rst	Thu Aug 25 20:05:30 2016 -0400
+++ b/Doc/library/sqlite3.rst	Fri Aug 26 14:12:15 2016 +0800
@@ -285,9 +285,9 @@
 
       .. versionadded:: 3.2
 
-   .. method:: cursor([cursorClass])
+   .. method:: cursor(factory=sqlite3.Cursor)
 
-      The cursor method accepts a single optional parameter *cursorClass*. If
+      The cursor method accepts a single keyword parameter *factory*. If
       supplied, this must be a custom cursor class that extends
       :class:`sqlite3.Cursor`.
 
diff -r 10a73648c92c Lib/sqlite3/test/factory.py
--- a/Lib/sqlite3/test/factory.py	Thu Aug 25 20:05:30 2016 -0400
+++ b/Lib/sqlite3/test/factory.py	Fri Aug 26 14:12:15 2016 +0800
@@ -60,6 +60,11 @@
     def CheckIsInstance(self):
         cur = self.con.cursor(factory=MyCursor)
         self.assertIsInstance(cur, MyCursor)
+        cur = self.con.cursor()
+        self.assertIsInstance(cur, sqlite.Cursor)
+
+    def CheckInvalidFactory(self):
+        self.assertRaises(TypeError, self.con.cursor, 'abcdef')
 
 class RowFactoryTestsBackwardsCompat(unittest.TestCase):
     def setUp(self):
@@ -185,7 +190,7 @@
         # segmentation fault.
         class FakeCursor(str):
             __class__ = sqlite.Cursor
-        cur = self.con.cursor(factory=FakeCursor)
+        cur = FakeCursor()
         self.assertRaises(TypeError, sqlite.Row, cur, ())
 
     def tearDown(self):
diff -r 10a73648c92c Lib/sqlite3/test/regression.py
--- a/Lib/sqlite3/test/regression.py	Thu Aug 25 20:05:30 2016 -0400
+++ b/Lib/sqlite3/test/regression.py	Fri Aug 26 14:12:15 2016 +0800
@@ -152,6 +152,18 @@
         con = sqlite.connect(":memory:")
         setattr(con, "isolation_level", "\xe9")
 
+    def CheckSetIsolationLevelSegmentationFault(self):
+        """
+        See issue 27861.
+        """
+        class SubStr(str):
+            def __del__(self):
+                con.isolation_level = ""
+
+        con = sqlite.connect(":memory:")
+        con.isolation_level = SubStr("")
+        con.isolation_level = ""
+
     def CheckCursorConstructorCallCheck(self):
         """
         Verifies that cursor methods check whether base class __init__ was
diff -r 10a73648c92c Modules/_sqlite/connection.c
--- a/Modules/_sqlite/connection.c	Thu Aug 25 20:05:30 2016 -0400
+++ b/Modules/_sqlite/connection.c	Fri Aug 26 14:12:15 2016 +0800
@@ -300,7 +300,7 @@
 
 PyObject* pysqlite_connection_cursor(pysqlite_Connection* self, PyObject* args, PyObject* kwargs)
 {
-    static char *kwlist[] = {"factory", NULL, NULL};
+    static char *kwlist[] = {"factory", NULL};
     PyObject* factory = NULL;
     PyObject* cursor;
 
@@ -309,6 +309,15 @@
         return NULL;
     }
 
+    if (factory &&
+        _PyObject_RealIsSubclass(factory,
+                                 (PyObject *)&pysqlite_CursorType) <= 0) {
+        PyErr_Format(PyExc_TypeError,
+                     "factory must be %s",
+                     pysqlite_CursorType.tp_name);
+        return NULL;
+    }
+
     if (!pysqlite_check_thread(self) || !pysqlite_check_connection(self)) {
         return NULL;
     }
@@ -1171,7 +1180,7 @@
     PyObject* begin_statement;
     static PyObject* begin_word;
 
-    Py_XDECREF(self->isolation_level);
+    Py_CLEAR(self->isolation_level);
 
     if (self->begin_statement) {
         PyMem_Free(self->begin_statement);