diff --git a/CHANGELOG.md b/CHANGELOG.md
index 4c4e93e8..30d022db 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -9,6 +9,9 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 ### Changed
 - modifier escape now triggers a E_USER_NOTICE when an unsupported escape type is used https://github.com/smarty-php/smarty/pull/649
 
+### Fixed
+- Fixed render crash when using inline include with a string template https://github.com/smarty-php/smarty/issues/639
+
 ## [3.1.39] - 2021-02-17
 
 ### Security
diff --git a/libs/sysplugins/smarty_internal_template.php b/libs/sysplugins/smarty_internal_template.php
index bae22a7d..d6f24c8f 100644
--- a/libs/sysplugins/smarty_internal_template.php
+++ b/libs/sysplugins/smarty_internal_template.php
@@ -317,7 +317,7 @@ class Smarty_Internal_Template extends Smarty_Internal_TemplateBase
                 $tpl->template_resource = $template;
                 $tpl->cache_id = $cache_id;
                 $tpl->compile_id = $compile_id;
-                if (isset($uid)) {
+                if (isset($uid) && isset($tpl->compiled->file_dependency[ $uid ])) {
                     // for inline templates we can get all resource information from file dependency
                     list($filepath, $timestamp, $type) = $tpl->compiled->file_dependency[ $uid ];
                     $tpl->source = new Smarty_Template_Source($smarty, $filepath, $type, $filepath);