Issue #6271: mmap tried to close invalid file handle (-1) when annonymous.
(On Unix) Patch by STINNER Victor.
diff --git a/Misc/NEWS b/Misc/NEWS
index 8af9914..aabdc21 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -325,6 +325,9 @@
 Library
 -------
 
+- Issue #6271: mmap tried to close invalid file handle (-1) when annonymous.
+  (On Unix)
+
 - Issue #6215: All bug fixes and enhancements from the Python 3.1 io library
   (including the fast C implementation) have been backported to the standard
   ``io`` module.
diff --git a/Modules/mmapmodule.c b/Modules/mmapmodule.c
index f660d6b..e1970cb 100644
--- a/Modules/mmapmodule.c
+++ b/Modules/mmapmodule.c
@@ -158,7 +158,8 @@
 #endif /* MS_WINDOWS */
 
 #ifdef UNIX
-	(void) close(self->fd);
+	if (0 <= self->fd)
+		(void) close(self->fd);
 	self->fd = -1;
 	if (self->data != NULL) {
 		munmap(self->data, self->size);