diff --git a/src/ast/ast.cpp b/src/ast/ast.cpp
index 0780ecd0b..b7d401098 100644
--- a/src/ast/ast.cpp
+++ b/src/ast/ast.cpp
@@ -1420,6 +1420,7 @@ ast_manager::~ast_manager() {
                 mark.mark(to_quantifier(n)->get_expr(), true);
                 mark_array_ref(mark, to_quantifier(n)->get_num_patterns(), to_quantifier(n)->get_patterns());
                 mark_array_ref(mark, to_quantifier(n)->get_num_no_patterns(), to_quantifier(n)->get_no_patterns());
+                mark.mark(to_quantifier(n)->get_sort(), true);
                 break;
             }
         }