diff --git a/apps/federation/lib/DbHandler.php b/apps/federation/lib/DbHandler.php
index 3b88ffeabd55..0878e2471a82 100644
--- a/apps/federation/lib/DbHandler.php
+++ b/apps/federation/lib/DbHandler.php
@@ -293,6 +293,9 @@ protected function hash($url) {
 	 * @return string
 	 */
 	protected function normalizeUrl($url) {
+		if ($url === null) {
+			$url = '';
+		}
 		$normalized = $url;
 
 		if (\strpos($url, 'https://') === 0) {
diff --git a/changelog/unreleased/41597 b/changelog/unreleased/41597
new file mode 100644
index 000000000000..a6f1182b735c
--- /dev/null
+++ b/changelog/unreleased/41597
@@ -0,0 +1,7 @@
+Fix: Adjust code to avoid PHP8 messages
+
+Avoid trying to access array offset on false in the encryption storage wrapper.
+
+Handle passing null to normalizeUrl in the federation DbHandler.
+
+https://github.com/owncloud/core/pull/41597
diff --git a/lib/private/Files/Storage/Wrapper/Encryption.php b/lib/private/Files/Storage/Wrapper/Encryption.php
index d3697f1b9a5e..6131ec45b226 100644
--- a/lib/private/Files/Storage/Wrapper/Encryption.php
+++ b/lib/private/Files/Storage/Wrapper/Encryption.php
@@ -472,7 +472,7 @@ public function fopen($path, $mode) {
 					if (!empty($encryptionModuleId)) {
 						$encryptionModule = $this->encryptionManager->getEncryptionModule($encryptionModuleId);
 						$shouldEncrypt = true;
-					} elseif (empty($encryptionModuleId) && $info['encrypted'] === true) {
+					} elseif ($info !== false && $info->isEncrypted()) {
 						// we come from a old installation. No header and/or no module defined
 						// but the file is encrypted. In this case we need to use the
 						// OC_DEFAULT_MODULE to read the file