diff --git a/src/backend/access/nbtree/nbtsearch.c b/src/backend/access/nbtree/nbtsearch.c
index 15f3bec1ab0..e0bbb97cbec 100644
--- a/src/backend/access/nbtree/nbtsearch.c
+++ b/src/backend/access/nbtree/nbtsearch.c
@@ -1628,6 +1628,7 @@ _bt_readpage(IndexScanDesc scan, ScanDirection dir, OffsetNumber offnum,
 	 * corresponding need for the left-link, since splits always go right.
 	 */
 	so->currPos.nextPage = opaque->btpo_next;
+	so->currPos.dir = dir;
 
 	/* initialize tuple workspace to empty */
 	so->currPos.nextTupleOffset = 0;
@@ -2083,16 +2084,24 @@ _bt_steppage(IndexScanDesc scan, ScanDirection dir)
 		 * In effect, btrestpos leaves advancing the arrays up to the first
 		 * _bt_readpage call (that takes place after it has restored markPos).
 		 */
-		Assert(so->markPos.dir == dir);
 		if (so->needPrimScan)
 		{
-			if (ScanDirectionIsForward(dir))
+			if (ScanDirectionIsForward(so->currPos.dir))
 				so->markPos.moreRight = true;
 			else
 				so->markPos.moreLeft = true;
 		}
 	}
 
+	/*
+	 * Cancel primitive index scans that were scheduled when the call to
+	 * _bt_readpage for currPos happened to use the opposite direction to the
+	 * one that we're stepping in now.  (It's okay to leave the scan's array
+	 * keys as-is, since the next _bt_readpage will advance them.)
+	 */
+	if (so->currPos.dir != dir)
+		so->needPrimScan = false;
+
 	if (ScanDirectionIsForward(dir))
 	{
 		/* Walk right to the next page with data */
@@ -2653,7 +2662,6 @@ _bt_endpoint(IndexScanDesc scan, ScanDirection dir)
 static inline void
 _bt_initialize_more_data(BTScanOpaque so, ScanDirection dir)
 {
-	so->currPos.dir = dir;
 	if (so->needPrimScan)
 	{
 		Assert(so->numArrayKeys);
diff --git a/src/backend/access/nbtree/nbtutils.c b/src/backend/access/nbtree/nbtutils.c
index c22ccec789d..8d047d8873f 100644
--- a/src/backend/access/nbtree/nbtutils.c
+++ b/src/backend/access/nbtree/nbtutils.c
@@ -2426,8 +2426,10 @@ new_prim_scan:
 	/*
 	 * End this primitive index scan, but schedule another.
 	 *
-	 * Note: If the scan direction happens to change, this scheduled primitive
-	 * index scan won't go ahead after all.
+	 * Note: We make a soft assumption that the current scan direction will
+	 * also be used within _bt_next, when it is asked to step off this page.
+	 * It is up to _bt_next to cancel this scheduled primitive index scan
+	 * whenever it steps to a page in the direction opposite currPos.dir.
 	 */
 	pstate->continuescan = false;	/* Tell _bt_readpage we're done... */
 	so->needPrimScan = true;	/* ...but call _bt_first again */