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
@@ -648,7 +648,7 @@
                      STRING, ENDMARKER, ENCODING, tok_name, detect_encoding,
                      open as tokenize_open, Untokenizer)
 from io import BytesIO
-from unittest import TestCase
+from unittest import TestCase, mock
 import os, sys, glob
 import token
 
@@ -1032,6 +1032,15 @@
             self.assertEqual(fp.encoding, 'utf-8-sig')
             self.assertEqual(fp.mode, 'r')
 
+        # test close file of unrecognized encoding
+        m = mock.mock_open(read_data=b'#coding:xxx')
+        with mock.patch('tokenize._builtin_open', m):
+            try:
+                tokenize_open(filename)
+            except:
+                pass
+        self.assertTrue(m().close.called)
+
     def test_filename_in_exception(self):
         # When possible, include the file name in the exception.
         path = 'some_file_path'
diff --git a/Lib/tokenize.py b/Lib/tokenize.py
--- a/Lib/tokenize.py
+++ b/Lib/tokenize.py
@@ -435,7 +435,11 @@
     detect_encoding().
     """
     buffer = _builtin_open(filename, 'rb')
-    encoding, lines = detect_encoding(buffer.readline)
+    try:
+        encoding, lines = detect_encoding(buffer.readline)
+    except:
+        buffer.close()
+        raise
     buffer.seek(0)
     text = TextIOWrapper(buffer, encoding, line_buffering=True)
     text.mode = 'r'