diff --git a/lib/private/AllConfig.php b/lib/private/AllConfig.php
index e73e2fdef91b7..ba04068f12123 100644
--- a/lib/private/AllConfig.php
+++ b/lib/private/AllConfig.php
@@ -243,7 +243,7 @@ public function setUserValue($userId, $appName, $key, $value, $preCondition = nu
 			}
 		}
 
-		$userPreferences->setValueMixed($userId, $appName, $key, $value);
+		$userPreferences->setValueMixed($userId, $appName, $key, (string)$value);
 	}
 
 	/**
@@ -314,7 +314,14 @@ public function getAllUserValues(?string $userId): array {
 			return [];
 		}
 
-		return \OC::$server->get(UserPreferences::class)->getAllValues($userId);
+		$values = \OC::$server->get(UserPreferences::class)->getAllValues($userId);
+		$result = [];
+		foreach($values as $app => $list) {
+			foreach($list as $key => $value) {
+				$result[$app][$key] = (string)$value;
+			}
+		}
+		return $result;
 	}
 
 	/**
diff --git a/lib/private/UserPreferences.php b/lib/private/UserPreferences.php
index 8fe59b51d5b97..53a647a51de67 100644
--- a/lib/private/UserPreferences.php
+++ b/lib/private/UserPreferences.php
@@ -144,7 +144,7 @@ public function hasKey(string $userId, string $app, string $key, ?bool $lazy = f
 		$this->loadPreferences($userId, $lazy);
 
 		if ($lazy === null) {
-			$appCache = $this->getAllValues($userId, $app);
+			$appCache = $this->getValues($userId, $app);
 			return isset($appCache[$key]);
 		}
 
@@ -451,7 +451,7 @@ public function getValueMixed(
 		string $userId,
 		string $app,
 		string $key,
-		string $default = '',
+		?string $default = '',
 		?bool $lazy = false
 	): string {
 		try {