diff --git a/htdocs/core/class/conf.class.php b/htdocs/core/class/conf.class.php
index 16fe6c50aa1..c234a15a374 100644
--- a/htdocs/core/class/conf.class.php
+++ b/htdocs/core/class/conf.class.php
@@ -1257,7 +1257,7 @@ class Conf extends stdClass
 			if (!isset($this->MAIN_RESTRICTHTML_ONLY_VALID_HTML)) {
 				$this->global->MAIN_RESTRICTHTML_ONLY_VALID_HTML = 1;
 			}
-			if (!isset($this->MAIN_RESTRICTHTML_ONLY_VALID_HTML_TIDY)) {
+			if (!isset($this->MAIN_RESTRICTHTML_ONLY_VALID_HTML_TIDY) && extension_loaded('tidy') && class_exists("tidy")) {
 				$this->global->MAIN_RESTRICTHTML_ONLY_VALID_HTML_TIDY = 1;
 			}
 
diff --git a/test/phpunit/SecurityTest.php b/test/phpunit/SecurityTest.php
index 743b6d33c8e..4991e1d16bd 100644
--- a/test/phpunit/SecurityTest.php
+++ b/test/phpunit/SecurityTest.php
@@ -772,9 +772,11 @@ class SecurityTest extends CommonClassTest
 
 		// Set options for cleaning data
 		$conf->global->MAIN_RESTRICTHTML_ONLY_VALID_HTML = 0;	// disabled, does not work on HTML5 and some libxml versions
-		// Enabled option MAIN_RESTRICTHTML_ONLY_VALID_HTML_TIDY if possible
+		// Enable option MAIN_RESTRICTHTML_ONLY_VALID_HTML_TIDY if possible
 		if (extension_loaded('tidy') && class_exists("tidy")) {
 			$conf->global->MAIN_RESTRICTHTML_ONLY_VALID_HTML_TIDY = 1;
+		} else {
+			$conf->global->MAIN_RESTRICTHTML_ONLY_VALID_HTML_TIDY = 0;
 		}
 		$conf->global->MAIN_RESTRICTHTML_REMOVE_ALSO_BAD_ATTRIBUTES = 0;	// disabled, does not work on HTML5 and some libxml versions