diff --git a/src/backend/utils/sort/logtape.c b/src/backend/utils/sort/logtape.c
index 666a7c0e81c..c09e1e308ae 100644
--- a/src/backend/utils/sort/logtape.c
+++ b/src/backend/utils/sort/logtape.c
@@ -99,7 +99,7 @@ typedef struct TapeBlockTrailer
 								 * bytes on last block (if < 0) */
 } TapeBlockTrailer;
 
-#define TapeBlockPayloadSize  (BLCKSZ - sizeof(TapeBlockTrailer))
+#define TapeBlockPayloadSize  (BLCKSZ - 16)
 #define TapeBlockGetTrailer(buf) \
 	((TapeBlockTrailer *) ((char *) buf + TapeBlockPayloadSize))