diff --git a/src/Core/Config/Cache/PConfigCache.php b/src/Core/Config/Cache/PConfigCache.php
index d6b1c9b316..b0dd209cbf 100644
--- a/src/Core/Config/Cache/PConfigCache.php
+++ b/src/Core/Config/Cache/PConfigCache.php
@@ -36,6 +36,10 @@ class PConfigCache
 	 */
 	public function load($uid, array $config)
 	{
+		if (!is_int($uid)) {
+			return;
+		}
+
 		$categories = array_keys($config);
 
 		foreach ($categories as $category) {
@@ -64,6 +68,10 @@ class PConfigCache
 	 */
 	public function get($uid, string $cat, string $key = null)
 	{
+		if (!is_int($uid)) {
+			return null;
+		}
+
 		if (isset($this->config[$uid][$cat][$key])) {
 			return $this->config[$uid][$cat][$key];
 		} elseif (!isset($key) && isset($this->config[$uid][$cat])) {
@@ -87,6 +95,10 @@ class PConfigCache
 	 */
 	public function set($uid, string $cat, string $key, $value)
 	{
+		if (!is_int($uid)) {
+			return false;
+		}
+
 		if (!isset($this->config[$uid]) || !is_array($this->config[$uid])) {
 			$this->config[$uid] = [];
 		}
@@ -118,6 +130,10 @@ class PConfigCache
 	 */
 	public function delete($uid, string $cat, string $key)
 	{
+		if (!is_int($uid)) {
+			return false;
+		}
+
 		if (isset($this->config[$uid][$cat][$key])) {
 			unset($this->config[$uid][$cat][$key]);
 			if (count($this->config[$uid][$cat]) == 0) {
diff --git a/tests/src/Core/Config/Cache/PConfigCacheTest.php b/tests/src/Core/Config/Cache/PConfigCacheTest.php
index 22beccf601..283a5bc6ab 100644
--- a/tests/src/Core/Config/Cache/PConfigCacheTest.php
+++ b/tests/src/Core/Config/Cache/PConfigCacheTest.php
@@ -255,4 +255,21 @@ class PConfigCacheTest extends MockedTest
 		$this->assertNull($configCache->get(1, 'cat2', 'key2'));
 		$this->assertNull($configCache->get(2, 'cat1', 'key1'));
 	}
+
+	/**
+	 * Test when using an invalid UID
+	 * @todo check it the clean way before using the config class
+	 */
+	public function testInvalidUid()
+	{
+		// bad UID!
+		$uid = null;
+
+		$configCache = new PConfigCache();
+
+		$this->assertNull($configCache->get($uid, 'cat1', 'cat2'));
+
+		$this->assertFalse($configCache->set($uid, 'cat1', 'key1', 'doesn\'t matter!'));
+		$this->assertFalse($configCache->delete($uid, 'cat1', 'key1'));
+	}
 }