diff -r a16403affccd Lib/test/test_io.py
--- a/Lib/test/test_io.py	Wed Aug 01 03:57:52 2012 +0200
+++ b/Lib/test/test_io.py	Wed Aug 01 05:16:30 2012 +0200
@@ -2720,6 +2720,12 @@
         support.gc_collect()
         self.assertTrue(wr() is None, wr)
 
+    def test_buffer_freeing(self) :
+        f = open(__file__, "rb")
+        f_size = sys.getsizeof(f)
+        f.close()
+        self.assertGreater(f_size, sys.getsizeof(f))
+
     def test_abcs(self):
         # Test the visible base classes are ABCs.
         self.assertIsInstance(self.IOBase, abc.ABCMeta)
diff -r a16403affccd Misc/NEWS
--- a/Misc/NEWS	Wed Aug 01 03:57:52 2012 +0200
+++ b/Misc/NEWS	Wed Aug 01 05:16:30 2012 +0200
@@ -53,6 +53,9 @@
 - Issue #15291: Fix a memory leak where AST nodes where not properly
   deallocated.
 
+- Issue #15448: Buffered IO now frees the buffer when closed, instead
+  of when deallocating.
+
 - Issue #15110: Fix the tracebacks generated by "import xxx" to not show
   the importlib stack frames.
 
diff -r a16403affccd Modules/_io/bufferedio.c
--- a/Modules/_io/bufferedio.c	Wed Aug 01 03:57:52 2012 +0200
+++ b/Modules/_io/bufferedio.c	Wed Aug 01 05:16:30 2012 +0200
@@ -519,6 +519,11 @@
 
     res = PyObject_CallMethodObjArgs(self->raw, _PyIO_str_close, NULL);
 
+    if (self->buffer) {
+        PyMem_Free(self->buffer);
+        self->buffer = NULL;
+    }
+
 end:
     LEAVE_BUFFERED(self)
     return res;