diff --git a/src/backend/utils/sort/tuplesort.c b/src/backend/utils/sort/tuplesort.c
index 7ca517b357..ea8af9f79b 100644
--- a/src/backend/utils/sort/tuplesort.c
+++ b/src/backend/utils/sort/tuplesort.c
@@ -1788,7 +1788,7 @@ inittapes(Tuplesortstate *state)
 	 * account for tuple space, so we don't care if LACKMEM becomes
 	 * inaccurate.)
 	 */
-	tapeSpace = maxTapes * TAPE_BUFFER_OVERHEAD;
+	tapeSpace = (int64) maxTapes * TAPE_BUFFER_OVERHEAD;
 	if (tapeSpace + GetMemoryChunkSpace(state->memtuples) < state->allowedMem)
 		USEMEM(state, tapeSpace);