diff --git a/CHANGELOG.md b/CHANGELOG.md
index 57ef12da5..cfc7fb5a5 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -13,6 +13,7 @@
     * Fixed broken list in `bin/gpm index` [#3092](https://github.com/getgrav/grav/issues/3092)
     * Fixed CLI/GPM command failures returning 0 (success) value [#3017](https://github.com/getgrav/grav/issues/3017)
     * Fixed unimplemented `PageObject::getOriginal()` call [#3098](https://github.com/getgrav/grav/issues/3098)
+    * Fixed `Argument 1 passed to Grav\Common\User\DataUser\User::filterUsername() must be of the type string` [#1992](https://github.com/getgrav/grav-plugin-admin/issues/1992)
 
 # v1.7.0-rc.19
 ## 12/02/2020
diff --git a/system/src/Grav/Common/Flex/Types/Users/UserCollection.php b/system/src/Grav/Common/Flex/Types/Users/UserCollection.php
index 527d973ff..53faa8a29 100644
--- a/system/src/Grav/Common/Flex/Types/Users/UserCollection.php
+++ b/system/src/Grav/Common/Flex/Types/Users/UserCollection.php
@@ -43,6 +43,8 @@ class UserCollection extends FlexCollection implements UserCollectionInterface
      */
     public function load($username): UserInterface
     {
+        $username = (string)$username;
+
         if ($username !== '') {
             $key = $this->filterUsername($username);
             $user = $this->get($key);
diff --git a/system/src/Grav/Common/Flex/Types/Users/UserIndex.php b/system/src/Grav/Common/Flex/Types/Users/UserIndex.php
index d51d7f450..7711b192e 100644
--- a/system/src/Grav/Common/Flex/Types/Users/UserIndex.php
+++ b/system/src/Grav/Common/Flex/Types/Users/UserIndex.php
@@ -79,6 +79,8 @@ class UserIndex extends FlexIndex
      */
     public function load($username): UserInterface
     {
+        $username = (string)$username;
+
         if ($username !== '') {
             $key = static::filterUsername($username, $this->getFlexDirectory()->getStorage());
             $user = $this->get($key);
diff --git a/system/src/Grav/Common/User/DataUser/User.php b/system/src/Grav/Common/User/DataUser/User.php
index 745513dbf..0f328c801 100644
--- a/system/src/Grav/Common/User/DataUser/User.php
+++ b/system/src/Grav/Common/User/DataUser/User.php
@@ -120,7 +120,7 @@ class User extends Data implements UserInterface
         }
 
         if ($file) {
-            $username = $this->filterUsername($this->get('username'));
+            $username = $this->filterUsername((string)$this->get('username'));
 
             if (!$file->filename()) {
                 $locator = Grav::instance()['locator'];
diff --git a/system/src/Grav/Common/User/DataUser/UserCollection.php b/system/src/Grav/Common/User/DataUser/UserCollection.php
index 557e1fb79..2f921d414 100644
--- a/system/src/Grav/Common/User/DataUser/UserCollection.php
+++ b/system/src/Grav/Common/User/DataUser/UserCollection.php
@@ -48,6 +48,8 @@ class UserCollection implements UserCollectionInterface
      */
     public function load($username): UserInterface
     {
+        $username = (string)$username;
+
         $grav = Grav::instance();
         /** @var UniformResourceLocator $locator */
         $locator = $grav['locator'];