diff --git a/Doc/whatsnew/3.13.rst b/Doc/whatsnew/3.13.rst
index 34dd3ea8858ea2..84d5daae6e623c 100644
--- a/Doc/whatsnew/3.13.rst
+++ b/Doc/whatsnew/3.13.rst
@@ -1120,7 +1120,8 @@ Porting to Python 3.13
 * ``Python.h`` no longer includes the ``<unistd.h>`` standard header file. If
   needed, it should now be included explicitly. For example, it provides the
   functions: ``read()``, ``write()``, ``close()``, ``isatty()``, ``lseek()``,
-  ``getpid()``, ``getcwd()``, ``sysconf()`` and ``getpagesize()``.
+  ``getpid()``, ``getcwd()``, ``sysconf()``, ``getpagesize()``, ``alarm()`` and
+  ``pause()``.
   As a consequence, ``_POSIX_SEMAPHORES`` and ``_POSIX_THREADS`` macros are no
   longer defined by ``Python.h``. The ``HAVE_UNISTD_H`` and ``HAVE_PTHREAD_H``
   macros defined by ``Python.h`` can be used to decide if ``<unistd.h>`` and
diff --git a/Modules/signalmodule.c b/Modules/signalmodule.c
index 2932d94858afde..56ddc5ea283d93 100644
--- a/Modules/signalmodule.c
+++ b/Modules/signalmodule.c
@@ -21,6 +21,7 @@
 #  include "socketmodule.h"       // SOCKET_T
 #endif
 
+#include <unistd.h>               // alarm()
 #ifdef MS_WINDOWS
 #  ifdef HAVE_PROCESS_H
 #    include <process.h>