diff --git a/src/backend/utils/sort/tuplesort.c b/src/backend/utils/sort/tuplesort.c
index cf1cdcb..bd8c0ee 100644
--- a/src/backend/utils/sort/tuplesort.c
+++ b/src/backend/utils/sort/tuplesort.c
@@ -201,6 +201,7 @@ typedef enum
  * tape during a preread cycle (see discussion at top of file).
  */
 #define MINORDER		6		/* minimum merge order */
+#define MAXORDER		250		/* maximum merge order */
 #define TAPE_BUFFER_OVERHEAD		(BLCKSZ * 3)
 #define MERGE_BUFFER_SIZE			(BLCKSZ * 32)
 
@@ -2066,8 +2067,15 @@ tuplesort_merge_order(int64 allowedMem)
 	mOrder = (allowedMem - TAPE_BUFFER_OVERHEAD) /
 		(MERGE_BUFFER_SIZE + TAPE_BUFFER_OVERHEAD);
 
-	/* Even in minimum memory, use at least a MINORDER merge */
+	/*
+	 * Even in minimum memory, use at least a MINORDER merge.  At the same
+	 * time, cap the maximum merge order quasi-arbitrarily.  With more than
+	 * several hundred tapes, the overhead per-tape is likely to become a
+	 * concern, since that will only happen in the event of severe memory
+	 * pressure.
+	 */
 	mOrder = Max(mOrder, MINORDER);
+	mOrder = Min(mOrder, MAXORDER);
 
 	return mOrder;
 }