diff --git a/CHANGELOG.md b/CHANGELOG.md
index 4c4e93e89..30d022db7 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 bae22a7d5..d6f24c8ff 100644
--- a/libs/sysplugins/smarty_internal_template.php
+++ b/libs/sysplugins/smarty_internal_template.php
@@ -317,7 +317,7 @@ public function _subTemplateRender(
                 $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);
diff --git a/tests/UnitTests/TemplateSource/TagTests/Include/CompileIncludeTest.php b/tests/UnitTests/TemplateSource/TagTests/Include/CompileIncludeTest.php
index 830089aef..c07f11007 100644
--- a/tests/UnitTests/TemplateSource/TagTests/Include/CompileIncludeTest.php
+++ b/tests/UnitTests/TemplateSource/TagTests/Include/CompileIncludeTest.php
@@ -324,4 +324,12 @@ public function dataTestSpacing()
                      array("A{include file='include_spacing3.tpl'}B\nC", "AbarB\nC", '3_Newline3', $i++),
         );
     }
+
+	/**
+	 * Test Inline Include with string template
+	 */
+	public function testInlineStringInclude()
+	{
+		$this->assertEquals('include-inline', $this->smarty->fetch('inline_string_include.tpl'));
+	}
 }
diff --git a/tests/UnitTests/TemplateSource/TagTests/Include/templates/inline_string_include.tpl b/tests/UnitTests/TemplateSource/TagTests/Include/templates/inline_string_include.tpl
new file mode 100644
index 000000000..44d7eb3a6
--- /dev/null
+++ b/tests/UnitTests/TemplateSource/TagTests/Include/templates/inline_string_include.tpl
@@ -0,0 +1 @@
+{include "string:include-inline" inline}
\ No newline at end of file