diff --git a/system/blueprints/flex/accounts.yaml b/system/blueprints/flex/accounts.yaml
index 14fd36b07..52eff696d 100644
--- a/system/blueprints/flex/accounts.yaml
+++ b/system/blueprints/flex/accounts.yaml
@@ -2,7 +2,7 @@ title: Flex User Accounts
 description: Manage your User Accounts in Flex.
 type: flex-objects
 
-# Deprecated in Grav 1.7.0-rc.4: file was renamed.
+# Deprecated in Grav 1.7.0-rc.4: file was renamed to user-accounts.yaml
 extends@:
   type: user-accounts
   context: blueprints://flex
diff --git a/system/blueprints/flex/user-accounts.yaml b/system/blueprints/flex/user-accounts.yaml
index bf978f397..56aad88bb 100644
--- a/system/blueprints/flex/user-accounts.yaml
+++ b/system/blueprints/flex/user-accounts.yaml
@@ -113,6 +113,7 @@ config:
         pattern: '{FOLDER}/{KEY}{EXT}'
         indexed: true
         key: username
+        case_sensitive: false
     search:
       options:
         contains: 1
diff --git a/system/src/Grav/Common/Flex/Types/Users/Storage/UserFileStorage.php b/system/src/Grav/Common/Flex/Types/Users/Storage/UserFileStorage.php
index 30b4b7467..ec61532bb 100644
--- a/system/src/Grav/Common/Flex/Types/Users/Storage/UserFileStorage.php
+++ b/system/src/Grav/Common/Flex/Types/Users/Storage/UserFileStorage.php
@@ -15,6 +15,21 @@ use Grav\Framework\Flex\Storage\FileStorage;
 
 class UserFileStorage extends FileStorage
 {
+    public $caseSensitive;
+
+    /**
+     * @param string $key
+     * @return string
+     */
+    public function normalizeKey(string $key): string
+    {
+        if ($this->caseSensitive === true) {
+            return $key;
+        }
+
+        return mb_strtolower($key);
+    }
+
     /**
      * {@inheritdoc}
      * @see FlexStorageInterface::getMediaPath()
@@ -40,4 +55,15 @@ class UserFileStorage extends FileStorage
             $row['access'] = $access;
         }
     }
+
+    /**
+     * @param array $options
+     * @return void
+     */
+    protected function initOptions(array $options): void
+    {
+        parent::initOptions($options);
+
+        $this->caseSensitive = $options['case_sensitive'] ?? false;
+    }
 }
diff --git a/system/src/Grav/Common/Flex/Types/Users/Storage/UserFolderStorage.php b/system/src/Grav/Common/Flex/Types/Users/Storage/UserFolderStorage.php
index 911ec5222..579e02bb5 100644
--- a/system/src/Grav/Common/Flex/Types/Users/Storage/UserFolderStorage.php
+++ b/system/src/Grav/Common/Flex/Types/Users/Storage/UserFolderStorage.php
@@ -15,6 +15,21 @@ use Grav\Framework\Flex\Storage\FolderStorage;
 
 class UserFolderStorage extends FolderStorage
 {
+    public $caseSensitive;
+
+    /**
+     * @param string $key
+     * @return string
+     */
+    public function normalizeKey(string $key): string
+    {
+        if ($this->caseSensitive === true) {
+            return $key;
+        }
+
+        return mb_strtolower($key);
+    }
+
     /**
      * Prepares the row for saving and returns the storage key for the record.
      *
@@ -30,4 +45,15 @@ class UserFolderStorage extends FolderStorage
             $row['access'] = $access;
         }
     }
+
+    /**
+     * @param array $options
+     * @return void
+     */
+    protected function initOptions(array $options): void
+    {
+        parent::initOptions($options);
+
+        $this->caseSensitive = $options['case_sensitive'] ?? false;
+    }
 }
diff --git a/system/src/Grav/Common/Flex/Types/Users/UserCollection.php b/system/src/Grav/Common/Flex/Types/Users/UserCollection.php
index 4874c68f9..70bc68555 100644
--- a/system/src/Grav/Common/Flex/Types/Users/UserCollection.php
+++ b/system/src/Grav/Common/Flex/Types/Users/UserCollection.php
@@ -43,7 +43,7 @@ class UserCollection extends FlexCollection implements UserCollectionInterface
     public function load($username): UserInterface
     {
         if ($username !== '') {
-            $key = mb_strtolower($username);
+            $key = $this->filterUsername($username);
             $user = $this->get($key);
             if ($user) {
                 return $user;
@@ -84,7 +84,7 @@ class UserCollection extends FlexCollection implements UserCollectionInterface
                 } elseif ($field === 'flex_key') {
                     $user = $this->withKeyField('flex_key')->get($query);
                 } elseif ($field === 'username') {
-                    $user = $this->get(mb_strtolower($query));
+                    $user = $this->get($this->filterUsername($query));
                 } else {
                     $user = parent::find($query, $field);
                 }
@@ -114,4 +114,18 @@ class UserCollection extends FlexCollection implements UserCollectionInterface
 
         return $exists;
     }
+
+    /**
+     * @param string $key
+     * @return bool|false|string|string[]|null
+     */
+    protected function filterUsername(string $key)
+    {
+        $storage = $this->getFlexDirectory()->getStorage();
+        if (method_exists($storage, 'normalizeKey')) {
+            return $storage->normalizeKey($key);
+        }
+
+        return mb_strtolower($key);
+    }
 }
diff --git a/system/src/Grav/Common/Flex/Types/Users/UserIndex.php b/system/src/Grav/Common/Flex/Types/Users/UserIndex.php
index 56c95376f..06d6851be 100644
--- a/system/src/Grav/Common/Flex/Types/Users/UserIndex.php
+++ b/system/src/Grav/Common/Flex/Types/Users/UserIndex.php
@@ -53,12 +53,13 @@ class UserIndex extends FlexIndex
     /**
      * @param array $meta
      * @param array $data
+     * @param FlexStorageInterface $storage
      */
-    public static function updateObjectMeta(array &$meta, array $data)
+    public static function updateObjectMeta(array &$meta, array $data, FlexStorageInterface $storage)
     {
         // Username can also be number and stored as such.
         $key = (string)($data['username'] ?? $meta['key'] ?? $meta['storage_key']);
-        $meta['key'] = mb_strtolower($key);
+        $meta['key'] = static::filterUsername($key, $storage);
         $meta['email'] = isset($data['email']) ? mb_strtolower($data['email']) : null;
     }
 
@@ -73,7 +74,7 @@ class UserIndex extends FlexIndex
     public function load($username): UserInterface
     {
         if ($username !== '') {
-            $key = mb_strtolower($username);
+            $key = static::filterUsername($username, $this->getFlexDirectory()->getStorage());
             $user = $this->get($key);
             if ($user) {
                 return $user;
@@ -116,7 +117,7 @@ class UserIndex extends FlexIndex
                 } elseif ($field === 'email') {
                     $user = $this->withKeyField('email')->get($query);
                 } elseif ($field === 'username') {
-                    $user = $this->get(mb_strtolower($query));
+                    $user = $this->get(static::filterUsername($query, $this->getFlexDirectory()->getStorage()));
                 } else {
                     $user = $this->__call('find', [$query, $field]);
                 }
@@ -129,6 +130,20 @@ class UserIndex extends FlexIndex
         return $this->load('');
     }
 
+    /**
+     * @param string $key
+     * @param FlexStorageInterface $storage
+     * @return string
+     */
+    protected static function filterUsername(string $key, FlexStorageInterface $storage): string
+    {
+        if ($storage && \method_exists($storage, 'normalizeKey')) {
+            return $storage->normalizeKey($key);
+        }
+
+        return mb_strtolower($key);
+    }
+
     /**
      * @param FlexStorageInterface $storage
      * @return CompiledYamlFile|null
diff --git a/system/src/Grav/Common/User/DataUser/User.php b/system/src/Grav/Common/User/DataUser/User.php
index 8428ab5d9..1c82b442d 100644
--- a/system/src/Grav/Common/User/DataUser/User.php
+++ b/system/src/Grav/Common/User/DataUser/User.php
@@ -116,11 +116,11 @@ class User extends Data implements UserInterface
         }
 
         if ($file) {
-            $username = $this->get('username');
+            $username = $this->filterUsername($this->get('username'));
 
             if (!$file->filename()) {
                 $locator = Grav::instance()['locator'];
-                $file->filename($locator->findResource('account://' . mb_strtolower($username) . YAML_EXT, true, true));
+                $file->filename($locator->findResource('account://' . $username . YAML_EXT, true, true));
             }
 
             // if plain text password, hash it and remove plain text
@@ -176,6 +176,8 @@ class User extends Data implements UserInterface
 
     /**
      * Serialize user.
+     *
+     * @return array
      */
     public function __sleep()
     {
@@ -272,6 +274,18 @@ class User extends Data implements UserInterface
         return parent::count();
     }
 
+    /**
+     * @param string $username
+     * @return string
+     */
+    protected function filterUsername(string $username): string
+    {
+        return mb_strtolower($username);
+    }
+
+    /**
+     * @return string|null
+     */
     protected function getAvatarFile(): ?string
     {
         $avatars = $this->get('avatar');
diff --git a/system/src/Grav/Common/User/DataUser/UserCollection.php b/system/src/Grav/Common/User/DataUser/UserCollection.php
index 55a0968df..4d10a2aa8 100644
--- a/system/src/Grav/Common/User/DataUser/UserCollection.php
+++ b/system/src/Grav/Common/User/DataUser/UserCollection.php
@@ -45,8 +45,8 @@ class UserCollection implements UserCollectionInterface
         /** @var UniformResourceLocator $locator */
         $locator = $grav['locator'];
 
-        // force lowercase of username
-        $username = mb_strtolower($username);
+        // Filter username.
+        $username = $this->filterUsername($username);
 
         $filename = 'account://' . $username . YAML_EXT;
         $path = $locator->findResource($filename) ?: $locator->findResource($filename, true, true);
@@ -138,4 +138,14 @@ class UserCollection implements UserCollectionInterface
 
         return count($accounts);
     }
+
+    /**
+     * @param string $username
+     * @return string
+     */
+    protected function filterUsername(string $username): string
+    {
+        return mb_strtolower($username);
+    }
+
 }
diff --git a/system/src/Grav/Framework/Flex/FlexIndex.php b/system/src/Grav/Framework/Flex/FlexIndex.php
index aebd1d937..ded360b1a 100644
--- a/system/src/Grav/Framework/Flex/FlexIndex.php
+++ b/system/src/Grav/Framework/Flex/FlexIndex.php
@@ -20,7 +20,6 @@ use Grav\Framework\Flex\Interfaces\FlexCollectionInterface;
 use Grav\Framework\Flex\Interfaces\FlexIndexInterface;
 use Grav\Framework\Flex\Interfaces\FlexObjectInterface;
 use Grav\Framework\Flex\Interfaces\FlexStorageInterface;
-use Grav\Framework\Object\Interfaces\ObjectCollectionInterface;
 use Grav\Framework\Object\Interfaces\ObjectInterface;
 use Grav\Framework\Object\ObjectIndex;
 use Monolog\Logger;
@@ -77,8 +76,9 @@ class FlexIndex extends ObjectIndex implements FlexCollectionInterface, FlexInde
      *
      * @param array $meta
      * @param array $data
+     * @param FlexStorageInterface $storage
      */
-    public static function updateObjectMeta(array &$meta, array $data)
+    public static function updateObjectMeta(array &$meta, array $data, FlexStorageInterface $storage)
     {
         // For backwards compatibility, no need to call this method when you override this method.
         static::updateIndexData($meta, $data);
@@ -709,7 +709,7 @@ class FlexIndex extends ObjectIndex implements FlexCollectionInterface, FlexInde
                     if ($keyField !== 'storage_key' && isset($row[$keyField])) {
                         $entry['key'] = $row[$keyField];
                     }
-                    static::updateObjectMeta($entry, $row ?? []);
+                    static::updateObjectMeta($entry, $row ?? [], $storage);
                     if (isset($row['__ERROR'])) {
                         $entry['__ERROR'] = true;
                         static::onException(new \RuntimeException(sprintf('Object failed to load: %s (%s)', $key,
diff --git a/system/src/Grav/Framework/Flex/FlexObject.php b/system/src/Grav/Framework/Flex/FlexObject.php
index 0ab04747e..842bbc801 100644
--- a/system/src/Grav/Framework/Flex/FlexObject.php
+++ b/system/src/Grav/Framework/Flex/FlexObject.php
@@ -623,7 +623,7 @@ class FlexObject implements FlexObjectInterface, FlexAuthorizeInterface
         if ($meta) {
             /** @var FlexIndex $indexClass */
             $indexClass = $this->getFlexDirectory()->getIndexClass();
-            $indexClass::updateObjectMeta($meta, $value);
+            $indexClass::updateObjectMeta($meta, $value, $storage);
             $this->_meta = $meta;
         }