diff -r cecec75c2250 Lib/csv.py
--- a/Lib/csv.py	Thu Sep 05 16:06:46 2013 +0200
+++ b/Lib/csv.py	Thu Sep 05 22:36:59 2013 +0800
@@ -46,7 +46,7 @@
     def _validate(self):
         try:
             _Dialect(self)
-        except TypeError as e:
+        except (TypeError, ValueError) as e:
             # We do this for compatibility with py2.3
             raise Error(str(e))
 
diff -r cecec75c2250 Lib/test/test_csv.py
--- a/Lib/test/test_csv.py	Thu Sep 05 16:06:46 2013 +0200
+++ b/Lib/test/test_csv.py	Thu Sep 05 22:36:59 2013 +0800
@@ -22,7 +22,7 @@
         self.assertRaises(TypeError, ctor, None)
         self.assertRaises(TypeError, ctor, arg, bad_attr = 0)
         self.assertRaises(TypeError, ctor, arg, delimiter = 0)
-        self.assertRaises(TypeError, ctor, arg, delimiter = 'XX')
+        self.assertRaises(ValueError, ctor, arg, delimiter = 'XX')
         self.assertRaises(csv.Error, ctor, arg, 'foo')
         self.assertRaises(TypeError, ctor, arg, delimiter=None)
         self.assertRaises(TypeError, ctor, arg, delimiter=1)
@@ -743,7 +743,7 @@
             skipinitialspace = True
             lineterminator = '\r\n'
             quoting = csv.QUOTE_NONE
-        d = mydialect()
+        mydialect()
 
         mydialect.quoting = None
         self.assertRaises(csv.Error, mydialect)
@@ -751,13 +751,19 @@
         mydialect.doublequote = True
         mydialect.quoting = csv.QUOTE_ALL
         mydialect.quotechar = '"'
-        d = mydialect()
+        mydialect()
 
         mydialect.quotechar = "''"
-        self.assertRaises(csv.Error, mydialect)
+        with self.assertRaises(csv.Error) as cm:
+            mydialect()
+        self.assertEqual(str(cm.exception),
+                         '"quotechar" must be an 1-character string')
 
         mydialect.quotechar = 4
-        self.assertRaises(csv.Error, mydialect)
+        with self.assertRaises(csv.Error) as cm:
+            mydialect()
+        self.assertEqual(str(cm.exception),
+                         '"quotechar" must be string, not int')
 
     def test_delimiter(self):
         class mydialect(csv.Dialect):
@@ -767,13 +773,25 @@
             skipinitialspace = True
             lineterminator = '\r\n'
             quoting = csv.QUOTE_NONE
-        d = mydialect()
+        mydialect()
 
         mydialect.delimiter = ":::"
-        self.assertRaises(csv.Error, mydialect)
+        with self.assertRaises(csv.Error) as cm:
+            mydialect()
+        self.assertEqual(str(cm.exception),
+                         '"delimiter" must be an 1-character string')
+
+        mydialect.delimiter = b","
+        with self.assertRaises(csv.Error) as cm:
+            mydialect()
+        self.assertEqual(str(cm.exception),
+                         '"delimiter" must be string, not bytes')
 
         mydialect.delimiter = 4
-        self.assertRaises(csv.Error, mydialect)
+        with self.assertRaises(csv.Error) as cm:
+            mydialect()
+        self.assertEqual(str(cm.exception),
+                         '"delimiter" must be string, not int')
 
     def test_lineterminator(self):
         class mydialect(csv.Dialect):
@@ -783,13 +801,16 @@
             skipinitialspace = True
             lineterminator = '\r\n'
             quoting = csv.QUOTE_NONE
-        d = mydialect()
+        mydialect()
 
         mydialect.lineterminator = ":::"
-        d = mydialect()
+        mydialect()
 
         mydialect.lineterminator = 4
-        self.assertRaises(csv.Error, mydialect)
+        with self.assertRaises(csv.Error) as cm:
+            mydialect()
+        self.assertEqual(str(cm.exception),
+                         '"lineterminator" must be a string')
 
 
 class TestSniffer(unittest.TestCase):
diff -r cecec75c2250 Modules/_csv.c
--- a/Modules/_csv.c	Thu Sep 05 16:06:46 2013 +0200
+++ b/Modules/_csv.c	Thu Sep 05 22:36:59 2013 +0800
@@ -239,11 +239,16 @@
         *target = '\0';
         if (src != Py_None) {
             Py_ssize_t len;
+            if (!PyUnicode_Check(src)) {
+                PyErr_Format(PyExc_TypeError,
+                    "\"%s\" must be string, not %s", name,
+                    src->ob_type->tp_name);
+                return -1;
+            }
             len = PyUnicode_GetLength(src);
             if (len > 1) {
-                PyErr_Format(PyExc_TypeError,
-                    "\"%s\" must be an 1-character string",
-                    name);
+                PyErr_Format(PyExc_ValueError,
+                    "\"%s\" must be an 1-character string", name);
                 return -1;
             }
             /* PyUnicode_READY() is called in PyUnicode_GetLength() */