diff --git a/src/backend/storage/smgr/md.c b/src/backend/storage/smgr/md.c
index 2981b41..3774fb0 100644
--- a/src/backend/storage/smgr/md.c
+++ b/src/backend/storage/smgr/md.c
@@ -1159,6 +1159,7 @@ mdsync(void)
 			while ((segno = bms_first_member(requests)) >= 0)
 			{
 				int			failures;
+				bool		opened_directly = false;

 				/*
 				 * If fsync is off then we don't have to bother opening the
@@ -1223,6 +1224,23 @@ mdsync(void)

 					INSTR_TIME_SET_CURRENT(sync_start);

+					/*
+					 * _mdfd_getseg() will only open segments which aren't
+					 * preceded by non-truncated segments (c.f. notes about
+					 * RELSEG_SIZE at the top of this file). But there are
+					 * some cases, e.g. mdtruncate, where truncated segments
+					 * are to be fsynced: Thus open those explicitly here.  We
+					 * avoid always using _mdfd_openseg() because using
+					 * _mdfd_getseg() avoids some open()/close() calls if the
+					 * underlying files are already open.
+					 */
+					if (seg == NULL)
+					{
+						seg = _mdfd_openseg(reln, forknum, segno,
+											EXTENSION_RETURN_NULL);
+						opened_directly = true;
+					}
+
 					if (seg != NULL &&
 						FileSync(seg->mdfd_vfd) >= 0)
 					{
@@ -1241,6 +1259,13 @@ mdsync(void)
 								 FilePathName(seg->mdfd_vfd),
 								 (double) elapsed / 1000);

+						/* free resources if explicitly opened above */
+						if (opened_directly)
+						{
+							if (seg->mdfd_vfd >= 0)
+								FileClose(seg->mdfd_vfd);
+							pfree(seg);
+						}
 						break;	/* out of retry loop */
 					}