diff --git a/.github/workflows/build.yml b/.github/workflows/build.yml
index 7392021..a62a999 100644
--- a/.github/workflows/build.yml
+++ b/.github/workflows/build.yml
@@ -33,7 +33,7 @@ jobs:
       os: >-
         ['ubuntu-latest', 'windows-latest']
       php: >-
-        ['8.0', '8.1', '8.2', '8.3']
+        ['8.0', '8.1', '8.2', '8.3', '8.4']
   phpunit-with-intl:
     uses: yiisoft/actions/.github/workflows/phpunit.yml@master
     secrets:
@@ -45,4 +45,4 @@ jobs:
       os: >-
         ['ubuntu-latest', 'windows-latest']
       php: >-
-        ['8.0', '8.1', '8.2', '8.3']
+        ['8.0', '8.1', '8.2', '8.3', '8.4']
diff --git a/.github/workflows/composer-require-checker.yml b/.github/workflows/composer-require-checker.yml
index a857bce..a93390b 100644
--- a/.github/workflows/composer-require-checker.yml
+++ b/.github/workflows/composer-require-checker.yml
@@ -31,4 +31,4 @@ jobs:
       os: >-
         ['ubuntu-latest']
       php: >-
-        ['8.1', '8.2', '8.3']
+        ['8.1', '8.2', '8.3', '8.4']
diff --git a/.github/workflows/rector.yml b/.github/workflows/rector.yml
index 457772a..5d6931d 100644
--- a/.github/workflows/rector.yml
+++ b/.github/workflows/rector.yml
@@ -21,4 +21,4 @@ jobs:
       os: >-
         ['ubuntu-latest']
       php: >-
-        ['8.3']
+        ['8.4']
diff --git a/.github/workflows/static.yml b/.github/workflows/static.yml
index d2a03af..64b476e 100644
--- a/.github/workflows/static.yml
+++ b/.github/workflows/static.yml
@@ -30,7 +30,7 @@ jobs:
       os: >-
         ['ubuntu-latest']
       php: >-
-        ['8.1', '8.2', '8.3']
+        ['8.1', '8.2', '8.3', '8.4']
   psalm80:
     uses: yiisoft/actions/.github/workflows/psalm.yml@master
     with:
diff --git a/CHANGELOG.md b/CHANGELOG.md
index 14e3357..a855bf9 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -3,6 +3,7 @@
 ## 3.1.1 under development
 
 - New #149: Add `InMemoryMessageSource` (@vjik)
+- Chg #150: Change PHP constraint in `composer.json` to `8.0 - 8.4` (@vjik)
 
 ## 3.1.0 December 26, 2024
 
diff --git a/composer.json b/composer.json
index f5867b5..72fde60 100644
--- a/composer.json
+++ b/composer.json
@@ -28,19 +28,19 @@
         }
     ],
     "require": {
-        "php": "^8.0",
+        "php": "8.0 - 8.4",
         "psr/event-dispatcher": "1.0.0",
-        "yiisoft/files": "^1.0|^2.0",
+        "yiisoft/files": "^1.0 || ^2.0",
         "yiisoft/i18n": "^1.0"
     },
     "require-dev": {
-        "maglnet/composer-require-checker": "^4.2",
-        "phpunit/phpunit": "^9.6",
-        "rector/rector": "^2.0.3",
+        "maglnet/composer-require-checker": "^4.4",
+        "phpunit/phpunit": "^9.6.22",
+        "rector/rector": "^2.0.10",
         "roave/infection-static-analysis-plugin": "^1.25",
-        "spatie/phpunit-watcher": "^1.23",
-        "vimeo/psalm": "^4.30|^5.21",
-        "yiisoft/di": "^1.2"
+        "spatie/phpunit-watcher": "^1.23.6",
+        "vimeo/psalm": "^4.30 || ^5.26.1 || ^6.8.9",
+        "yiisoft/di": "^1.2.1"
     },
     "suggest": {
         "ext-intl": "Allows using intl message formatter",
diff --git a/psalm.xml b/psalm.xml
index b48c894..2b2e0b2 100644
--- a/psalm.xml
+++ b/psalm.xml
@@ -3,6 +3,7 @@
     errorLevel="1"
     findUnusedBaselineEntry="true"
     findUnusedCode="false"
+    ensureOverrideAttribute="false"
     xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
     xmlns="https://getpsalm.org/schema/config"
     xsi:schemaLocation="https://getpsalm.org/schema/config vendor/vimeo/psalm/config.xsd"
diff --git a/src/Extractor/TranslationExtractor.php b/src/Extractor/TranslationExtractor.php
index eebf2c6..2bb2541 100644
--- a/src/Extractor/TranslationExtractor.php
+++ b/src/Extractor/TranslationExtractor.php
@@ -77,6 +77,9 @@ public function extract(string $defaultCategory = 'app', ?string $translatorCall
         ]);
 
         foreach ($files as $file) {
+            /**
+             * @var string $fileContent We assume that `file_get_contents` can always read the file.
+             */
             $fileContent = file_get_contents($file);
             $messages = array_merge_recursive($messages, $parser->extract($fileContent));
             if ($parser->hasSkippedLines()) {
diff --git a/src/SimpleMessageFormatter.php b/src/SimpleMessageFormatter.php
index cab22d6..ed2c8c1 100644
--- a/src/SimpleMessageFormatter.php
+++ b/src/SimpleMessageFormatter.php
@@ -10,6 +10,9 @@
 use function in_array;
 use function is_int;
 
+/**
+ * @final
+ */
 class SimpleMessageFormatter implements MessageFormatterInterface
 {
     /**
diff --git a/src/Translator.php b/src/Translator.php
index f496f08..221964a 100644
--- a/src/Translator.php
+++ b/src/Translator.php
@@ -20,12 +20,12 @@ final class Translator implements TranslatorInterface
 
     /**
      * @var array Array of category message sources indexed by category names.
-     * @psalm-var array<string,CategorySource[]>
+     * @psalm-var array<string, non-empty-list<CategorySource>>
      */
     private array $categorySources = [];
 
     /**
-     * @psalm-var array<string,true>
+     * @psalm-var array<string, true>
      */
     private array $dispatchedMissingTranslationCategoryEvents = [];