Index: Modules/mmapmodule.c
===================================================================
--- Modules/mmapmodule.c	(revision 87937)
+++ Modules/mmapmodule.c	(working copy)
@@ -1192,12 +1192,7 @@
         }
 #endif
     } else {
-        m_obj->fd = dup(fd);
-        if (m_obj->fd == -1) {
-            Py_DECREF(m_obj);
-            PyErr_SetFromErrno(mmap_module_error);
-            return NULL;
-        }
+        m_obj->fd = fd
     }
 
     m_obj->data = mmap(NULL, map_size,