diff --git a/ext/random/engine_mt19937.c b/ext/random/engine_mt19937.c
index 6400999091038..b76e89ac1d6eb 100644
--- a/ext/random/engine_mt19937.c
+++ b/ext/random/engine_mt19937.c
@@ -392,11 +392,11 @@ PHP_METHOD(Random_Engine_Mt19937, __debugInfo)
 
 	if (engine->engine.algo->serialize) {
 		array_init(&t);
+		zend_hash_str_add(Z_ARR_P(return_value), "__states", strlen("__states"), &t);
 		if (!engine->engine.algo->serialize(engine->engine.state, Z_ARRVAL(t))) {
 			zend_throw_exception(NULL, "Engine serialize failed", 0);
 			RETURN_THROWS();
 		}
-		zend_hash_str_add(Z_ARR_P(return_value), "__states", strlen("__states"), &t);
 	}
 }
 /* }}} */