diff --git a/src/backend/optimizer/path/clausesel.c b/src/backend/optimizer/path/clausesel.c
index 2540da9..ddfdc3b 100644
--- a/src/backend/optimizer/path/clausesel.c
+++ b/src/backend/optimizer/path/clausesel.c
@@ -279,6 +279,10 @@ clauselist_selectivity(PlannerInfo *root,
 		List *solution = choose_mv_statistics(root, relid, stats,
 											  clauses, conditions);
 
+		/* FIXME we must not scribble over the original list */
+		if (solution)
+			clauses = list_copy(clauses);
+
 		/*
 		 * We have a good solution, which is merely a list of statistics that
 		 * we need to apply. We'll apply the statistics one by one (in the order