diff --git a/Misc/NEWS b/Misc/NEWS
index 94bf2b9de07..7d1317d0429 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -29,6 +29,9 @@ Extensions
 Library
 -------
 
+- Issue #9448: Fix a leak of OS resources (mutexes or semaphores) when
+  re-initializing a buffered IO object by calling its ``__init__`` method.
+
 - Issue #1713: Fix os.path.ismount(), which returned true for symbolic links
   across devices.
 
diff --git a/Modules/_io/bufferedio.c b/Modules/_io/bufferedio.c
index 07fe0a1d81d..1dd1ec4ba94 100644
--- a/Modules/_io/bufferedio.c
+++ b/Modules/_io/bufferedio.c
@@ -636,6 +636,8 @@ _buffered_init(buffered *self)
         return -1;
     }
 #ifdef WITH_THREAD
+    if (self->lock)
+        PyThread_free_lock(self->lock);
     self->lock = PyThread_allocate_lock();
     if (self->lock == NULL) {
         PyErr_SetString(PyExc_RuntimeError, "can't allocate read lock");