diff --git a/lib/Property/ICalendar/CalAddress.php b/lib/Property/ICalendar/CalAddress.php
index 2dbbc6eaf..c190f4750 100644
--- a/lib/Property/ICalendar/CalAddress.php
+++ b/lib/Property/ICalendar/CalAddress.php
@@ -53,7 +53,11 @@ public function getNormalizedValue()
             return $input;
         }
         list($schema, $everythingElse) = explode(':', $input, 2);
+        $schema = strtolower($schema);
+        if($schema == "mailto") {
+            $everythingElse = strtolower($everythingElse);
+        }
 
-        return strtolower($schema).':'.$everythingElse;
+        return $schema.':'.$everythingElse;
     }
 }
diff --git a/tests/VObject/Property/ICalendar/CalAddressTest.php b/tests/VObject/Property/ICalendar/CalAddressTest.php
index a907daf5c..e7490869f 100644
--- a/tests/VObject/Property/ICalendar/CalAddressTest.php
+++ b/tests/VObject/Property/ICalendar/CalAddressTest.php
@@ -25,6 +25,8 @@ public function values()
         return [
             ['mailto:a@b.com', 'mailto:a@b.com'],
             ['mailto:a@b.com', 'MAILTO:a@b.com'],
+            ['mailto:a@b.com', 'mailto:A@B.COM'],
+            ['mailto:a@b.com', 'MAILTO:A@B.COM'],
             ['/foo/bar', '/foo/bar'],
         ];
     }