diff --git a/src/backend/access/transam/xlogfuncs.c b/src/backend/access/transam/xlogfuncs.c
index 45a70668b1..5039052263 100644
--- a/src/backend/access/transam/xlogfuncs.c
+++ b/src/backend/access/transam/xlogfuncs.c
@@ -378,6 +378,8 @@ pg_last_wal_replay_lsn(PG_FUNCTION_ARGS)
  * Note that a location exactly at a segment boundary is taken to be in
  * the previous segment.  This is usually the right thing, since the
  * expected usage is to determine which xlog file(s) are ready to archive.
+ * To be consistent to filename, returns the offset one byte before the given
+ * location as offset.
  */
 Datum
 pg_walfile_name_offset(PG_FUNCTION_ARGS)
@@ -411,10 +413,13 @@ pg_walfile_name_offset(PG_FUNCTION_ARGS)
 
 	resultTupleDesc = BlessTupleDesc(resultTupleDesc);
 
+	/* We assume the desired location is one-byte before the LSN. */
+	locationpoint--;
+
 	/*
 	 * xlogfilename
 	 */
-	XLByteToPrevSeg(locationpoint, xlogsegno, wal_segment_size);
+	XLByteToSeg(locationpoint, xlogsegno, wal_segment_size);
 	XLogFileName(xlogfilename, GetWALInsertionTimeLine(), xlogsegno,
 				 wal_segment_size);