diff --git a/src/lti/LTI_Message_Launch.php b/src/lti/LTI_Message_Launch.php
index 7a18195d..9b9e3235 100644
--- a/src/lti/LTI_Message_Launch.php
+++ b/src/lti/LTI_Message_Launch.php
@@ -238,8 +238,8 @@ private function cache_launch_data() {
 
     private function validate_state() {
         // Check State for OIDC.
-        if ($this->cookie->get_cookie('lti1p3_' . $this->request['state']) !== $this->request['state']) {
-            // Error if state doesn't match
+        if (!isset($this->request['state']) || $this->cookie->get_cookie('lti1p3_' . $this->request['state']) !== $this->request['state']) {
+            // Error if state is not set, or doesn't match
             throw new LTI_Exception("State not found", 1);
         }
         return $this;
@@ -369,4 +369,4 @@ private function validate_message() {
 
     }
 }
-?>
\ No newline at end of file
+?>