diff --git a/src/backend/access/heap/pruneheap.c b/src/backend/access/heap/pruneheap.c
index c2f5343dac..5c20a7bc4c 100644
--- a/src/backend/access/heap/pruneheap.c
+++ b/src/backend/access/heap/pruneheap.c
@@ -733,7 +733,7 @@ heap_page_prune_execute(Buffer buffer,
  * root_offsets[k - 1] = j.
  *
  * The passed-in root_offsets array must have MaxHeapTuplesPerPage entries.
- * We zero out all unused entries.
+ * Unused entries are filled with InvalidOffsetNumber (zero).
  *
  * The function must be called with at least share lock on the buffer, to
  * prevent concurrent prune operations.
@@ -748,7 +748,8 @@ heap_get_root_tuples(Page page, OffsetNumber *root_offsets)
 	OffsetNumber offnum,
 				maxoff;
 
-	MemSet(root_offsets, 0, MaxHeapTuplesPerPage * sizeof(OffsetNumber));
+	MemSet(root_offsets, InvalidOffsetNumber,
+		   MaxHeapTuplesPerPage * sizeof(OffsetNumber));
 
 	maxoff = PageGetMaxOffsetNumber(page);
 	for (offnum = FirstOffsetNumber; offnum <= maxoff; offnum = OffsetNumberNext(offnum))
diff --git a/src/backend/catalog/index.c b/src/backend/catalog/index.c
index 061efd36a6..df52ee9a36 100644
--- a/src/backend/catalog/index.c
+++ b/src/backend/catalog/index.c
@@ -2714,6 +2714,12 @@ IndexBuildHeapRangeScan(Relation heapRelation,
 		 * buffer continuously while visiting the page, so no pruning
 		 * operation can occur either.
 		 *
+		 * In cases with only ShareUpdateExclusiveLock on the table, it's
+		 * possible for some HOT tuples to appear that we didn't know about
+		 * when we first read the page.  To handle that case, we re-obtain the
+		 * list of root offsets when a HOT tuple points to a root item that we
+		 * don't know about.
+		 *
 		 * Also, although our opinions about tuple liveness could change while
 		 * we scan the page (due to concurrent transaction commits/aborts),
 		 * the chain root locations won't, so this info doesn't need to be
@@ -3013,6 +3019,20 @@ IndexBuildHeapRangeScan(Relation heapRelation,
 			rootTuple = *heapTuple;
 			offnum = ItemPointerGetOffsetNumber(&heapTuple->t_self);
 
+			/*
+			 * If a HOT tuple points to a root that we don't know
+			 * about, obtain root items afresh.  If that still fails,
+			 * report it as corruption.
+			 */
+			if (root_offsets[offnum - 1] == InvalidOffsetNumber)
+			{
+				Page	page = BufferGetPage(scan->rs_cbuf);
+
+				LockBuffer(scan->rs_cbuf, BUFFER_LOCK_SHARE);
+				heap_get_root_tuples(page, root_offsets);
+				LockBuffer(scan->rs_cbuf, BUFFER_LOCK_UNLOCK);
+			}
+
 			if (!OffsetNumberIsValid(root_offsets[offnum - 1]))
 				ereport(ERROR,
 						(errcode(ERRCODE_DATA_CORRUPTED),