diff --git a/Lib/test/test_csv.py b/Lib/test/test_csv.py
index 6c1c542..f53c5ea 100644
--- a/Lib/test/test_csv.py
+++ b/Lib/test/test_csv.py
@@ -6,7 +6,7 @@
 import sys
 import os
 import unittest
-from io import StringIO
+from io import StringIO, BytesIO
 from tempfile import TemporaryFile
 import csv
 import gc
@@ -211,6 +211,10 @@
                           ['ab\0c'], None, strict = 1)
         self._read_test(['"ab"c'], [['abc']], doublequote = 0)
 
+        self.assertRaises(csv.Error, self._read_test,
+                          [b'ab\0c'], None)
+
+
     def test_read_eol(self):
         self._read_test(['a,b'], [['a','b']])
         self._read_test(['a,b\n'], [['a','b']])
@@ -375,7 +379,7 @@
 
 class TestCsvBase(unittest.TestCase):
     def readerAssertEqual(self, input, expected_result):
-        with TemporaryFile("w+") as fileobj:
+        with TemporaryFile("w+", newline='') as fileobj:
             fileobj.write(input)
             fileobj.seek(0)
             reader = csv.reader(fileobj, dialect = self.dialect)
diff --git a/Modules/_csv.c b/Modules/_csv.c
index 10cf96f..75cafb2 100644
--- a/Modules/_csv.c
+++ b/Modules/_csv.c
@@ -270,7 +270,7 @@
 			*target = NULL;
 		else if (!IS_BASESTRING(src)) {
 			PyErr_Format(PyExc_TypeError, 
-				     "\"%s\" must be an string", name);
+				     "\"%s\" must be a string", name);
 			return -1;
 		}
 		else {
@@ -793,6 +793,16 @@
 					     "newline inside string");
                         return NULL;
                 }
+		if (!PyUnicode_Check(lineobj))
+		{
+			PyErr_Format(error_obj,
+				     "Iterator should return strings, "
+				     "not %.200s "
+				     "(did you open the file in text mode?)",
+				     lineobj->ob_type->tp_name
+				);
+			return NULL;
+		}
                 ++self->line_num;
                 line = PyUnicode_AsUnicode(lineobj);
                 linelen = PyUnicode_GetSize(lineobj);