diff --git a/enumerator.c b/enumerator.c
index 358ec8a83d2f58..26bc9517cd74c0 100644
--- a/enumerator.c
+++ b/enumerator.c
@@ -311,7 +311,7 @@ static const rb_data_type_t proc_entry_data_type = {
         proc_entry_memsize,
         proc_entry_compact,
     },
-    0, 0, RUBY_TYPED_FREE_IMMEDIATELY
+    0, 0, RUBY_TYPED_FREE_IMMEDIATELY | RUBY_TYPED_WB_PROTECTED
 };
 
 static struct proc_entry *
@@ -1875,10 +1875,10 @@ lazy_add_method(VALUE obj, int argc, VALUE *argv, VALUE args, VALUE memo,
     VALUE entry_obj = TypedData_Make_Struct(rb_cObject, struct proc_entry,
                                             &proc_entry_data_type, entry);
     if (rb_block_given_p()) {
-        entry->proc = rb_block_proc();
+        RB_OBJ_WRITE(entry_obj, &entry->proc, rb_block_proc());
     }
     entry->fn = fn;
-    entry->memo = args;
+    RB_OBJ_WRITE(entry_obj, &entry->memo, args);
 
     lazy_set_args(entry_obj, memo);