rare, but still can happen

interpreter/code.c

@@ -548,9 +548,11 @@ void exec(Code* expr, int frame_ptr, int root_frame_ptr)
             }
             case FT_PRIM:
             {
+                int argmask = 1;
+                
                 for (int i = 0; i < thunk->desc->arity; i++) {
                     push_a(thunk->_args[i]);
-                    thunk->_args[i]->desc->eval();
+                    if(((PrimEntry*)thunk->desc)->boxingMap & argmask) thunk->_args[i]->desc->eval();
                     thunk = stack_a[root_frame_ptr-1];
                 }