diff --git a/php_array.h b/php_array.h
index bea5e59..0bbe0e6 100644
--- a/php_array.h
+++ b/php_array.h
@@ -370,7 +370,7 @@ char *php_array_zval_to_string(zval *z, int *plen, zend_bool *pfree) {
 			zval_copy_ctor(&c);
 			convert_to_string(&c);
 #ifdef ZEND_ENGINE_3
-			*pfree = ! IS_INTERNED(Z_STR(c));
+			*pfree = ! ZSTR_IS_INTERNED(Z_STR(c));
 #else
 			*pfree = ! IS_INTERNED(Z_STRVAL(c));
 #endif