diff --git a/src/backend/access/brin/brin_bloom.c b/src/backend/access/brin/brin_bloom.c
index 72aabbcf50..cc274256b3 100644
--- a/src/backend/access/brin/brin_bloom.c
+++ b/src/backend/access/brin/brin_bloom.c
@@ -661,6 +661,9 @@ brin_bloom_union(PG_FUNCTION_ARGS)
 	for (i = 0; i < nbytes; i++)
 		filter_a->data[i] |= filter_b->data[i];
 
+	/* update the number of bits set in the filter */
+	filter_a->nbits_set = pg_popcount((const char *) filter_a->data, nbytes);
+
 	PG_RETURN_VOID();
 }