@@ -51,6 +51,7 @@ Ankur Ankan
 Jon Anglin
 Heidi Annexstad
 Ramchandra Apte
+Arfrever Frehtes Taifersar Arahesis
 Éric Araujo
 Alicia Arlen
 Jeffrey Armstrong
 
@@ -27,6 +27,9 @@ Core and Builtins
 Library
 -------
 
+- Issue #21704: Fix build error for _multiprocessing when semaphores
+  are not available.  Patch by Arfrever Frehtes Taifersar Arahesis.
+
 - Fix repr(_socket.socket) on Windows 64-bit: don't fail with OverflowError
   on closed socket. repr(socket.socket) already works fine.
 
 
@@ -128,7 +128,9 @@ static PyMethodDef module_methods[] = {
     {"recv", multiprocessing_recv, METH_VARARGS, ""},
     {"send", multiprocessing_send, METH_VARARGS, ""},
 #endif
+#ifndef POSIX_SEMAPHORES_NOT_ENABLED
     {"sem_unlink", _PyMp_sem_unlink, METH_VARARGS, ""},
+#endif
     {NULL}
 };