diff --git a/src/backend/utils/adt/selfuncs.c b/src/backend/utils/adt/selfuncs.c
index 024f325eb02..26a2e3bb8b8 100644
--- a/src/backend/utils/adt/selfuncs.c
+++ b/src/backend/utils/adt/selfuncs.c
@@ -102,6 +102,7 @@
 #include <math.h>
 
 #include "access/brin.h"
+#include "access/brin_page.h"
 #include "access/gin.h"
 #include "access/table.h"
 #include "access/tableam.h"
@@ -6865,12 +6866,34 @@ brincostestimate(PlannerInfo *root, IndexPath *path, double loop_count,
 							  &spc_seq_page_cost);
 
 	/*
-	 * Obtain some data from the index itself.  A lock should have already
-	 * been obtained on the index in plancat.c.
+	 * Obtain some data from the index itself, if possible.  Otherwise invent
+	 * some plausible internal statistics based on the relation page count.
 	 */
-	indexRel = index_open(index->indexoid, NoLock);
-	brinGetStats(indexRel, &statsData);
-	index_close(indexRel, NoLock);
+	if (!index->hypothetical)
+	{
+		/*
+		 * A lock should have already been obtained on the index in plancat.c.
+		 */
+		indexRel = index_open(index->indexoid, NoLock);
+		brinGetStats(indexRel, &statsData);
+		index_close(indexRel, NoLock);
+
+		/* work out the actual number of ranges in the index */
+		indexRanges = Max(ceil((double) baserel->pages /
+							   statsData.pagesPerRange), 1.0);
+	}
+	else
+	{
+		/*
+		 * Assume default number of pages per range, and estimate the number
+		 * of ranges based on that.
+		 */
+		indexRanges = Max(ceil((double) baserel->pages /
+							   BRIN_DEFAULT_PAGES_PER_RANGE), 1.0);
+
+		statsData.pagesPerRange = BRIN_DEFAULT_PAGES_PER_RANGE;
+		statsData.revmapNumPages = (indexRanges / REVMAP_PAGE_MAXITEMS) + 1;
+	}
 
 	/*
 	 * Compute index correlation
@@ -6970,10 +6993,6 @@ brincostestimate(PlannerInfo *root, IndexPath *path, double loop_count,
 											 baserel->relid,
 											 JOIN_INNER, NULL);
 
-	/* work out the actual number of ranges in the index */
-	indexRanges = Max(ceil((double) baserel->pages / statsData.pagesPerRange),
-					  1.0);
-
 	/*
 	 * Now calculate the minimum possible ranges we could match with if all of
 	 * the rows were in the perfect order in the table's heap.