diff --git a/src/ast/ast.h b/src/ast/ast.h
index 2e054e371..0a3e90941 100644
--- a/src/ast/ast.h
+++ b/src/ast/ast.h
@@ -966,6 +966,7 @@ class ast_translation;
 
 class ast_table : public chashtable<ast*, obj_ptr_hash<ast>, ast_eq_proc> {
 public:
+    ast_table() : chashtable({}, {}, 512 * 1024, 8 * 1024) {}
     void push_erase(ast * n);
     ast* pop_erase();
 };