diff --git a/Include/pythread.h b/Include/pythread.h

index dfd6157..f3e6259 100644

--- a/Include/pythread.h

+++ b/Include/pythread.h

@@ -30,6 +30,8 @@ PyAPI_FUNC(void) PyThread_delete_key(int);

 PyAPI_FUNC(int) PyThread_set_key_value(int, void *);

 PyAPI_FUNC(void *) PyThread_get_key_value(int);

 PyAPI_FUNC(void) PyThread_delete_key_value(int key);

+PyAPI_FUNC(int) _PyThread_AcquireKeyLock(void);

+PyAPI_FUNC(void) _PyThread_ReleaseKeyLock(void);

 /* Cleanup after a fork */

 PyAPI_FUNC(void) PyThread_ReInitTLS(void);

diff --git a/Modules/posixmodule.c b/Modules/posixmodule.c

index 022d7aa..8f6cbb2 100644

--- a/Modules/posixmodule.c

+++ b/Modules/posixmodule.c

@@ -65,6 +65,10 @@ corresponding Unix manual entries for more information on calls.");

 #include "osdefs.h"

 #endif

+#ifdef WITH_THREAD

+#include "pythread.h"

+#endif

+

 #ifdef HAVE_SYS_TYPES_H

 #include <sys/types.h>

 #endif /* HAVE_SYS_TYPES_H */

@@ -3796,7 +3800,18 @@ posix_fork1(PyObject *self, PyObject *noargs)

     pid_t pid;

     int result = 0;

     _PyImport_AcquireLock();

+#ifdef WITH_THREAD

+    if (_PyThread_AcquireKeyLock() == 0) {

+        _PyImport_ReleaseLock();

+        PyErr_SetString(PyExc_RuntimeError,

+                        "could not acquire thread key lock");

+        return NULL;

+    }

+#endif

     pid = fork1();

+#ifdef WITH_THREAD

+    _PyThread_ReleaseKeyLock();

+#endif

     if (pid == 0) {

         /* child: this clobbers and resets the import lock. */

         PyOS_AfterFork();

@@ -3829,7 +3844,18 @@ posix_fork(PyObject *self, PyObject *noargs)

     pid_t pid;

     int result = 0;

     _PyImport_AcquireLock();

+#ifdef WITH_THREAD

+    if (_PyThread_AcquireKeyLock() == 0) {

+        _PyImport_ReleaseLock();

+        PyErr_SetString(PyExc_RuntimeError,

+                        "could not acquire thread key lock");

+        return NULL;

+    }

+#endif

     pid = fork();

+#ifdef WITH_THREAD

+    _PyThread_ReleaseKeyLock();

+#endif

     if (pid == 0) {

         /* child: this clobbers and resets the import lock. */

         PyOS_AfterFork();

@@ -3955,7 +3981,18 @@ posix_forkpty(PyObject *self, PyObject *noargs)

     pid_t pid;

     _PyImport_AcquireLock();

+#ifdef WITH_THREAD

+    if (_PyThread_AcquireKeyLock() == 0) {

+        _PyImport_ReleaseLock();

+        PyErr_SetString(PyExc_RuntimeError,

+                        "could not acquire thread key lock");

+        return NULL;

+    }

+#endif

     pid = forkpty(&master_fd, NULL, NULL, NULL);

+#ifdef WITH_THREAD

+    _PyThread_ReleaseKeyLock();

+#endif

     if (pid == 0) {

         /* child: this clobbers and resets the import lock. */

         PyOS_AfterFork();

diff --git a/Python/thread.c b/Python/thread.c

index dd333e8..957739e 100644

--- a/Python/thread.c

+++ b/Python/thread.c

@@ -387,6 +387,24 @@ PyThread_delete_key_value(int key)

     PyThread_release_lock(keymutex);

 }

+int

+_PyThread_AcquireKeyLock(void)

+{

+    if (keymutex == NULL) {

+        keymutex = PyThread_allocate_lock();

+    }

+    if (keymutex == NULL) {

+        return 0;

+    }

+    return PyThread_acquire_lock(keymutex, 1);

+}

+

+void

+_PyThread_ReleaseKeyLock(void)

+{

+    PyThread_release_lock(keymutex);

+}

+

 /* Forget everything not associated with the current thread id.

  * This function is called from PyOS_AfterFork().  It is necessary

  * because other thread ids which were in use at the time of the fork