diff --git a/plaintext_encoder.info.yml b/plaintext_encoder.info.yml
index 6ffc47141fbff3f3efc71e65c913d937ad0dcfc1..02d1fd591b2ace417aec478880a8f97ecd752535 100644
--- a/plaintext_encoder.info.yml
+++ b/plaintext_encoder.info.yml
@@ -1,6 +1,5 @@
 name: 'Plaintext encoder'
 type: module
 description: 'Provides plaintext as a serialization format.'
-core: '8.x'
-core_version_requirement: ^8 || ^9
+core_version_requirement: ^8 || ^9 || ^10 || ^11
 package: Web services
diff --git a/src/Encoder/PlaintextEncoder.php b/src/Encoder/PlaintextEncoder.php
index e4849855ee9abfe05711acc504a8e5d7d1bdecda..b100be8991903498776b05032cc14e7796f6b706 100644
--- a/src/Encoder/PlaintextEncoder.php
+++ b/src/Encoder/PlaintextEncoder.php
@@ -27,14 +27,14 @@ class PlaintextEncoder implements EncoderInterface, DecoderInterface {
   /**
    * {@inheritdoc}
    */
-  public function supportsEncoding($format) {
+  public function supportsEncoding($format): bool {
     return $format == static::$format;
   }
 
   /**
    * {@inheritdoc}
    */
-  public function supportsDecoding($format) {
+  public function supportsDecoding($format): bool {
     return $format == static::$format;
   }
 
@@ -43,7 +43,7 @@ class PlaintextEncoder implements EncoderInterface, DecoderInterface {
    *
    * Uses HTML-safe strings, with several characters escaped.
    */
-  public function encode($data, $format, array $context = []) {
+  public function encode($data, $format, array $context = []): string {
     switch (gettype($data)) {
       case "array":
         break;
@@ -125,7 +125,7 @@ class PlaintextEncoder implements EncoderInterface, DecoderInterface {
   /**
    * {@inheritdoc}
    */
-  public function decode($data, $format, array $context = []) {
+  public function decode($data, $format, array $context = []): mixed {
     $results = [];
     return $results;
   }