diff --git a/src/Util/Bitmap.php b/src/Util/Bitmap.php
index 286e9b6a30..1d5956dde2 100644
--- a/src/Util/Bitmap.php
+++ b/src/Util/Bitmap.php
@@ -24,11 +24,11 @@ use App\Util\Exception\ServerException;
 abstract class Bitmap
 {
     /**
-     * Convert an to or from an integer and an array of constants for
-     * each bit. If $instance, return an object with the corresponding
+     * Convert from an integer to an onject or an array of constants for
+     * set each bit. If $instance, return an object with the corresponding
      * properties set
      */
-    private static function _do(int $r, bool $instance)
+    private static function _to(int $r, bool $instance)
     {
         $init  = $r;
         $class = get_called_class();
@@ -38,8 +38,12 @@ abstract class Bitmap
             $vals = [];
         }
 
-        $consts = (new \ReflectionClass($class))->getConstants();
-        unset($consts['PREFIX']);
+        $consts      = (new \ReflectionClass($class))->getConstants();
+        $have_prefix = false;
+        if (isset($consts['PREFIX'])) {
+            $have_prefix = true;
+            unset($consts['PREFIX']);
+        }
 
         foreach ($consts as $c => $v) {
             $b = ($r & $v) !== 0;
@@ -50,7 +54,7 @@ abstract class Bitmap
             if ($b) {
                 $r -= $v;
                 if (!$instance) {
-                    $vals[] = $class::PREFIX . $c;
+                    $vals[] = ($have_prefix ? $class::PREFIX : '') . $c;
                 }
             }
         }
@@ -69,11 +73,11 @@ abstract class Bitmap
 
     public static function create(int $r): self
     {
-        return self::_do($r, true);
+        return self::_to($r, true);
     }
 
     public static function toArray(int $r): array
     {
-        return self::_do($r, false);
+        return self::_to($r, false);
     }
 }
diff --git a/tests/Util/BitmapTest.php b/tests/Util/BitmapTest.php
new file mode 100644
index 0000000000..2178df2b5d
--- /dev/null
+++ b/tests/Util/BitmapTest.php
@@ -0,0 +1,59 @@
+<?php
+
+// {{{ License
+// This file is part of GNU social - https://www.gnu.org/software/social
+//
+// GNU social is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Affero General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// GNU social is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU Affero General Public License for more details.
+//
+// You should have received a copy of the GNU Affero General Public License
+// along with GNU social.  If not, see <http://www.gnu.org/licenses/>.
+// }}}
+
+namespace App\Tests\Util;
+
+use Symfony\Bundle\FrameworkBundle\Test\KernelTestCase;
+
+class FooBitmap extends \App\Util\Bitmap
+{
+    public const FOO  = 1;
+    public const BAR  = 2;
+    public const QUUX = 4;
+}
+
+class BarBitmap extends \App\Util\Bitmap
+{
+    public const HYDROGEN = 1;
+    public const HELIUM   = 2;
+    public const PREFIX   = 'BAR_';
+}
+
+class BitmapTest extends KernelTestCase
+{
+    public function testObj()
+    {
+        $a = FooBitmap::create(FooBitmap::FOO | FooBitmap::BAR);
+        static::assertTrue($a->foo);
+        static::assertTrue($a->bar);
+        static::assertFalse($a->quux);
+    }
+
+    public function testArray()
+    {
+        $b = FooBitmap::toArray(FooBitmap::FOO | FooBitmap::QUUX);
+        static::assertSame(['FOO', 'QUUX'], $b);
+    }
+
+    public function testPrefix()
+    {
+        $b = BarBitmap::toArray(BarBitmap::HYDROGEN | BarBitmap::HELIUM);
+        static::assertSame(['BAR_HYDROGEN', 'BAR_HELIUM'], $b);
+    }
+}