--- a/src/backend/utils/adt/rangetypes_selfuncs.c
+++ b/src/backend/utils/adt/rangetypes_selfuncs.c
@@ -1050,6 +1050,7 @@ calc_hist_selectivity_contained(TypeCacheEntry *typcache,
    double      dist;
    double      length_hist_frac;
    bool        final_bin = false;
+   Assert(i == upper_index);