diff -r 6dbc4d6ff31e Lib/mimetypes.py
--- a/Lib/mimetypes.py	Tue Aug 06 16:03:33 2013 +0200
+++ b/Lib/mimetypes.py	Tue Aug 06 23:29:15 2013 +0800
@@ -358,12 +358,12 @@
 
 def read_mime_types(file):
     try:
-        f = open(file)
+        with open(file) as f:
+            db = MimeTypes()
+            db.readfp(f, True)
+            return db.types_map[True]
     except OSError:
         return None
-    db = MimeTypes()
-    db.readfp(f, True)
-    return db.types_map[True]
 
 
 def _default_mime_types():
diff -r 6dbc4d6ff31e Lib/test/test_mimetypes.py
--- a/Lib/test/test_mimetypes.py	Tue Aug 06 16:03:33 2013 +0200
+++ b/Lib/test/test_mimetypes.py	Tue Aug 06 23:29:15 2013 +0800
@@ -16,6 +16,9 @@
     def setUp(self):
         self.db = mimetypes.MimeTypes()
 
+    def tearDown(self):
+        support.unlink(support.TESTFN)
+
     def test_default_data(self):
         eq = self.assertEqual
         eq(self.db.guess_type("foo.html"), ("text/html", None))
@@ -40,6 +43,14 @@
            ("x-application/x-unittest", None))
         eq(self.db.guess_extension("x-application/x-unittest"), ".pyunit")
 
+    def test_read_mime_types(self):
+        with open(support.TESTFN, "w") as file:
+            file.write("x-application/mimea mimea\n")
+            file.write("application/mimeb mimeb\n")
+        mime_types = mimetypes.read_mime_types(support.TESTFN)
+        self.assertEqual(mime_types['.mimea'], 'x-application/mimea')
+        self.assertEqual(mime_types['.mimeb'], 'application/mimeb')
+
     def test_non_standard_types(self):
         eq = self.assertEqual
         # First try strict