diff --git a/src/BaseCollection.php b/src/BaseCollection.php
index f6fa9bbd4d..ad68dc81cc 100644
--- a/src/BaseCollection.php
+++ b/src/BaseCollection.php
@@ -48,25 +48,27 @@ class BaseCollection extends \ArrayIterator
 	/**
 	 * @inheritDoc
 	 */
-	public function offsetSet($offset, $value)
+	#[\ReturnTypeWillChange]
+	public function offsetSet($key, $value): void
 	{
-		if (is_null($offset)) {
+		if (is_null($key)) {
 			$this->totalCount++;
 		}
 
-		parent::offsetSet($offset, $value);
+		parent::offsetSet($key, $value);
 	}
 
 	/**
 	 * @inheritDoc
 	 */
-	public function offsetUnset($offset)
+	#[\ReturnTypeWillChange]
+	public function offsetUnset($key): void
 	{
-		if ($this->offsetExists($offset)) {
+		if ($this->offsetExists($key)) {
 			$this->totalCount--;
 		}
 
-		parent::offsetUnset($offset);
+		parent::offsetUnset($key);
 	}
 
 	/**
diff --git a/src/Core/Session/Handler/Database.php b/src/Core/Session/Handler/Database.php
index 41ccb6b33f..337397be60 100644
--- a/src/Core/Session/Handler/Database.php
+++ b/src/Core/Session/Handler/Database.php
@@ -57,6 +57,7 @@ class Database extends AbstractSessionHandler
 		return true;
 	}
 
+	#[\ReturnTypeWillChange]
 	public function read($id)
 	{
 		if (empty($id)) {
@@ -136,6 +137,7 @@ class Database extends AbstractSessionHandler
 		}
 	}
 
+	#[\ReturnTypeWillChange]
 	public function gc($max_lifetime): bool
 	{
 		try {
diff --git a/src/Object/Email.php b/src/Object/Email.php
index 4d5a11715c..fdde4e96dd 100644
--- a/src/Object/Email.php
+++ b/src/Object/Email.php
@@ -200,6 +200,7 @@ class Email implements IEmail
 	/**
 	 * @inheritDoc
 	 */
+	#[\ReturnTypeWillChange]
 	public function jsonSerialize()
 	{
 		return $this->toArray();