diff --git a/contrib/amcheck/verify_nbtree.c b/contrib/amcheck/verify_nbtree.c
index aac8c74f546..825b677c47c 100644
--- a/contrib/amcheck/verify_nbtree.c
+++ b/contrib/amcheck/verify_nbtree.c
@@ -1597,8 +1597,7 @@ bt_target_page_check(BtreeCheckState *state)
 		 */
 		lowersizelimit = skey->heapkeyspace &&
 			(P_ISLEAF(topaque) || BTreeTupleGetHeapTID(itup) == NULL);
-		if (tupsize > (lowersizelimit ? BTMaxItemSize(state->target) :
-					   BTMaxItemSizeNoHeapTid(state->target)))
+		if (tupsize > (lowersizelimit ? BTMaxItemSize : BTMaxItemSizeNoHeapTid))
 		{
 			ItemPointer tid = BTreeTupleGetPointsToTID(itup);
 			char	   *itid,
diff --git a/src/backend/access/nbtree/nbtdedup.c b/src/backend/access/nbtree/nbtdedup.c
index cbe73675f86..08884116aec 100644
--- a/src/backend/access/nbtree/nbtdedup.c
+++ b/src/backend/access/nbtree/nbtdedup.c
@@ -84,7 +84,7 @@ _bt_dedup_pass(Relation rel, Buffer buf, IndexTuple newitem, Size newitemsz,
 	state = (BTDedupState) palloc(sizeof(BTDedupStateData));
 	state->deduplicate = true;
 	state->nmaxitems = 0;
-	state->maxpostingsize = Min(BTMaxItemSize(page) / 2, INDEX_SIZE_MASK);
+	state->maxpostingsize = Min(BTMaxItemSize / 2, INDEX_SIZE_MASK);
 	/* Metadata about base tuple of current pending posting list */
 	state->base = NULL;
 	state->baseoff = InvalidOffsetNumber;
@@ -568,7 +568,7 @@ _bt_dedup_finish_pending(Page newpage, BTDedupState state)
 		/* Use original, unchanged base tuple */
 		tuplesz = IndexTupleSize(state->base);
 		Assert(tuplesz == MAXALIGN(IndexTupleSize(state->base)));
-		Assert(tuplesz <= BTMaxItemSize(newpage));
+		Assert(tuplesz <= BTMaxItemSize);
 		if (PageAddItem(newpage, (Item) state->base, tuplesz, tupoff,
 						false, false) == InvalidOffsetNumber)
 			elog(ERROR, "deduplication failed to add tuple to page");
@@ -588,7 +588,7 @@ _bt_dedup_finish_pending(Page newpage, BTDedupState state)
 		state->intervals[state->nintervals].nitems = state->nitems;
 
 		Assert(tuplesz == MAXALIGN(IndexTupleSize(final)));
-		Assert(tuplesz <= BTMaxItemSize(newpage));
+		Assert(tuplesz <= BTMaxItemSize);
 		if (PageAddItem(newpage, (Item) final, tuplesz, tupoff, false,
 						false) == InvalidOffsetNumber)
 			elog(ERROR, "deduplication failed to add tuple to page");
diff --git a/src/backend/access/nbtree/nbtinsert.c b/src/backend/access/nbtree/nbtinsert.c
index 31fe1c3adec..aa82cede30a 100644
--- a/src/backend/access/nbtree/nbtinsert.c
+++ b/src/backend/access/nbtree/nbtinsert.c
@@ -827,7 +827,7 @@ _bt_findinsertloc(Relation rel,
 	opaque = BTPageGetOpaque(page);
 
 	/* Check 1/3 of a page restriction */
-	if (unlikely(insertstate->itemsz > BTMaxItemSize(page)))
+	if (unlikely(insertstate->itemsz > BTMaxItemSize))
 		_bt_check_third_page(rel, heapRel, itup_key->heapkeyspace, page,
 							 insertstate->itup);
 
diff --git a/src/backend/access/nbtree/nbtsort.c b/src/backend/access/nbtree/nbtsort.c
index 7aba852db90..fa336ba0096 100644
--- a/src/backend/access/nbtree/nbtsort.c
+++ b/src/backend/access/nbtree/nbtsort.c
@@ -829,7 +829,7 @@ _bt_buildadd(BTWriteState *wstate, BTPageState *state, IndexTuple itup,
 	 * make use of the reserved space.  This should never fail on internal
 	 * pages.
 	 */
-	if (unlikely(itupsz > BTMaxItemSize(npage)))
+	if (unlikely(itupsz > BTMaxItemSize))
 		_bt_check_third_page(wstate->index, wstate->heap, isleaf, npage,
 							 itup);
 
@@ -1305,7 +1305,7 @@ _bt_load(BTWriteState *wstate, BTSpool *btspool, BTSpool *btspool2)
 				 */
 				dstate->maxpostingsize = MAXALIGN_DOWN((BLCKSZ * 10 / 100)) -
 					sizeof(ItemIdData);
-				Assert(dstate->maxpostingsize <= BTMaxItemSize((Page) state->btps_buf) &&
+				Assert(dstate->maxpostingsize <= BTMaxItemSize &&
 					   dstate->maxpostingsize <= INDEX_SIZE_MASK);
 				dstate->htids = palloc(dstate->maxpostingsize);
 
diff --git a/src/backend/access/nbtree/nbtutils.c b/src/backend/access/nbtree/nbtutils.c
index 693e43c674b..efe58beaaad 100644
--- a/src/backend/access/nbtree/nbtutils.c
+++ b/src/backend/access/nbtree/nbtutils.c
@@ -3245,7 +3245,7 @@ _bt_check_third_page(Relation rel, Relation heap, bool needheaptidspace,
 	itemsz = MAXALIGN(IndexTupleSize(newtup));
 
 	/* Double check item size against limit */
-	if (itemsz <= BTMaxItemSize(page))
+	if (itemsz <= BTMaxItemSize)
 		return;
 
 	/*
@@ -3253,7 +3253,7 @@ _bt_check_third_page(Relation rel, Relation heap, bool needheaptidspace,
 	 * index uses version 2 or version 3, or that page is an internal page, in
 	 * which case a slightly higher limit applies.
 	 */
-	if (!needheaptidspace && itemsz <= BTMaxItemSizeNoHeapTid(page))
+	if (!needheaptidspace && itemsz <= BTMaxItemSizeNoHeapTid)
 		return;
 
 	/*
@@ -3270,8 +3270,7 @@ _bt_check_third_page(Relation rel, Relation heap, bool needheaptidspace,
 			 errmsg("index row size %zu exceeds btree version %u maximum %zu for index \"%s\"",
 					itemsz,
 					needheaptidspace ? BTREE_VERSION : BTREE_NOVAC_VERSION,
-					needheaptidspace ? BTMaxItemSize(page) :
-					BTMaxItemSizeNoHeapTid(page),
+					needheaptidspace ? BTMaxItemSize : BTMaxItemSizeNoHeapTid,
 					RelationGetRelationName(rel)),
 			 errdetail("Index row references tuple (%u,%u) in relation \"%s\".",
 					   ItemPointerGetBlockNumber(BTreeTupleGetHeapTID(newtup)),
diff --git a/src/backend/access/nbtree/nbtxlog.c b/src/backend/access/nbtree/nbtxlog.c
index fadd0617955..d31dd56732d 100644
--- a/src/backend/access/nbtree/nbtxlog.c
+++ b/src/backend/access/nbtree/nbtxlog.c
@@ -483,7 +483,7 @@ btree_xlog_dedup(XLogReaderState *record)
 		state->deduplicate = true;	/* unused */
 		state->nmaxitems = 0;	/* unused */
 		/* Conservatively use larger maxpostingsize than primary */
-		state->maxpostingsize = BTMaxItemSize(page);
+		state->maxpostingsize = BTMaxItemSize;
 		state->base = NULL;
 		state->baseoff = InvalidOffsetNumber;
 		state->basetupsize = 0;
diff --git a/src/include/access/nbtree.h b/src/include/access/nbtree.h
index e4fdeca3402..0c43767f8c3 100644
--- a/src/include/access/nbtree.h
+++ b/src/include/access/nbtree.h
@@ -161,13 +161,13 @@ typedef struct BTMetaPageData
  * a heap index tuple to make space for a tiebreaker heap TID
  * attribute, which we account for here.
  */
-#define BTMaxItemSize(page) \
-	(MAXALIGN_DOWN((PageGetPageSize(page) - \
+#define BTMaxItemSize \
+	(MAXALIGN_DOWN((BLCKSZ - \
 					MAXALIGN(SizeOfPageHeaderData + 3*sizeof(ItemIdData)) - \
 					MAXALIGN(sizeof(BTPageOpaqueData))) / 3) - \
 					MAXALIGN(sizeof(ItemPointerData)))
-#define BTMaxItemSizeNoHeapTid(page) \
-	MAXALIGN_DOWN((PageGetPageSize(page) - \
+#define BTMaxItemSizeNoHeapTid \
+	MAXALIGN_DOWN((BLCKSZ - \
 				   MAXALIGN(SizeOfPageHeaderData + 3*sizeof(ItemIdData)) - \
 				   MAXALIGN(sizeof(BTPageOpaqueData))) / 3)