diff --git a/lib/moodlelib.php b/lib/moodlelib.php
index d22c8dad008..2f639c887d8 100644
--- a/lib/moodlelib.php
+++ b/lib/moodlelib.php
@@ -5920,7 +5920,7 @@ function email_should_be_diverted($email) {
 
     $patterns = array_map('trim', preg_split("/[\s,]+/", $CFG->divertallemailsexcept, -1, PREG_SPLIT_NO_EMPTY));
     foreach ($patterns as $pattern) {
-        if (preg_match("/$pattern/", $email)) {
+        if (preg_match("/{$pattern}/i", $email)) {
             return false;
         }
     }
diff --git a/lib/tests/moodlelib_test.php b/lib/tests/moodlelib_test.php
index f10155671b3..7aa43a8d5f2 100644
--- a/lib/tests/moodlelib_test.php
+++ b/lib/tests/moodlelib_test.php
@@ -3426,6 +3426,7 @@ EOF;
                     'foo@example.com',
                     'test@real.com',
                     'fred.jones@example.com',
+                    'Fred.Jones@Example.com',
                 ),
                 true,
             ),
@@ -3435,6 +3436,7 @@ EOF;
                 array(
                     'dev1@dev.com',
                     'fred@example.com',
+                    'Fred@Example.com',
                     'fred+verp@example.com',
                 ),
                 false,