diff --git a/lib/SimpleSAML/SessionHandlerPHP.php b/lib/SimpleSAML/SessionHandlerPHP.php
index abdb0610dd67b3400fe7236be1a986f8e6656e09..8947296c37d422f4d0c3cccf72b0bb8481bf1493 100644
--- a/lib/SimpleSAML/SessionHandlerPHP.php
+++ b/lib/SimpleSAML/SessionHandlerPHP.php
@@ -323,7 +323,7 @@ class SimpleSAML_SessionHandlerPHP extends SimpleSAML_SessionHandler
 
         if ($cookieParams['secure'] && !\SimpleSAML\Utils\HTTP::isHTTPS()) {
             throw new \SimpleSAML\Error\CannotSetCookie(
-                'Secure cookies not allowed on http.',
+                'Setting secure cookie on plain HTTP is not allowed.',
                 \SimpleSAML\Error\CannotSetCookie::SECURE_COOKIE
             );
         }