diff --git a/Lib/test/test_tokenize.py b/Lib/test/test_tokenize.py
--- a/Lib/test/test_tokenize.py
+++ b/Lib/test/test_tokenize.py
@@ -638,7 +638,7 @@
 from test import support
 from tokenize import (tokenize, _tokenize, untokenize, NUMBER, NAME, OP,
                      STRING, ENDMARKER, ENCODING, tok_name, detect_encoding,
-                     open as tokenize_open)
+                     TokenInfo, open as tokenize_open)
 from io import BytesIO
 from unittest import TestCase
 import os, sys, glob
@@ -1109,6 +1109,45 @@
                                   token.NAME, token.AMPER, token.NUMBER,
                                   token.RPAR)
 
+    def test_untokenize_with_iterator(self):
+        tokens = [
+                TokenInfo(ENCODING, 'utf-8', (0, 0), (0, 0), ''),
+                TokenInfo(ENDMARKER, '', (0, 0), (0, 0), ''),
+                ]
+        iter_tokens = iter(tokens)
+
+        expected = untokenize(tokens)
+        source = untokenize(iter_tokens)
+
+        self.assertEqual(source, expected)
+
+    def test_untokenize_compat_mode(self):
+        tokens = [
+                TokenInfo(ENCODING, 'utf-8', (0, 0), (0, 0), ''),
+                TokenInfo(ENDMARKER, '', (0, 0), (0, 0), ''),
+                ]
+        truncated = [tok[:2] for tok in tokens]
+
+        expected = untokenize(tokens)
+        source = untokenize(truncated)
+
+        self.assertEqual(source, expected)
+
+
+    def test_untokenize_compat_mode_with_iterator(self):
+        tokens = [
+                TokenInfo(ENCODING, 'utf-8', (0, 0), (0, 0), ''),
+                TokenInfo(ENDMARKER, '', (0, 0), (0, 0), ''),
+                ]
+        truncated = (tok[:2] for tok in tokens)
+        iter_tokens = iter(tokens)
+
+        expected = untokenize(iter_tokens)
+        source = untokenize(truncated)
+
+        self.assertEqual(source, expected)
+
+
 __test__ = {"doctests" : doctests, 'decistmt': decistmt}
 
 def test_main():
diff --git a/Lib/tokenize.py b/Lib/tokenize.py
--- a/Lib/tokenize.py
+++ b/Lib/tokenize.py
@@ -258,8 +258,10 @@
 
         if toknum in (NAME, NUMBER):
             tokval += ' '
-        if toknum in (NEWLINE, NL):
+        elif toknum in (NEWLINE, NL):
             startline = True
+        elif toknum == ENCODING:
+            self.encoding = tokval
         prevstring = False
         for tok in iterable:
             toknum, tokval = tok[:2]