diff --git a/composer.json b/composer.json
index 7c6269e2..7c9b9b98 100644
--- a/composer.json
+++ b/composer.json
@@ -27,7 +27,6 @@
     ],
     "require": {
         "php": "^8.0",
-        "ext-json": "*",
         "ext-phar": "*",
         "composer-runtime-api": "^2.0.0",
         "nikic/php-parser": "^4.13.0",
@@ -49,7 +48,8 @@
         "optimize-autoloader": true,
         "sort-packages": true,
         "allow-plugins": {
-            "dealerdirect/phpcodesniffer-composer-installer": true
+            "dealerdirect/phpcodesniffer-composer-installer": true,
+            "infection/extension-installer": true
         }
     },
     "extra": {
diff --git a/data/config.dist.json b/data/config.dist.json
index 1576e3f7..212d250f 100644
--- a/data/config.dist.json
+++ b/data/config.dist.json
@@ -7,6 +7,7 @@
   "php-core-extensions" : [
     "Core",
     "date",
+    "json",
     "pcre",
     "Phar",
     "Reflection",
diff --git a/src/ComposerRequireChecker/Cli/Options.php b/src/ComposerRequireChecker/Cli/Options.php
index 4f4b159a..2f244da7 100644
--- a/src/ComposerRequireChecker/Cli/Options.php
+++ b/src/ComposerRequireChecker/Cli/Options.php
@@ -41,6 +41,7 @@ class Options
     private array $phpCoreExtensions = [
         'Core',
         'date',
+        'json',
         'pcre',
         'Phar',
         'Reflection',
diff --git a/src/ComposerRequireChecker/DefinedExtensionsResolver/DefinedExtensionsResolver.php b/src/ComposerRequireChecker/DefinedExtensionsResolver/DefinedExtensionsResolver.php
index 1b1be2c7..9e82285e 100644
--- a/src/ComposerRequireChecker/DefinedExtensionsResolver/DefinedExtensionsResolver.php
+++ b/src/ComposerRequireChecker/DefinedExtensionsResolver/DefinedExtensionsResolver.php
@@ -8,7 +8,7 @@
 use function array_merge;
 use function file_get_contents;
 use function json_decode;
-use function strpos;
+use function str_starts_with;
 use function substr;
 
 class DefinedExtensionsResolver
@@ -32,7 +32,7 @@ public function __invoke(string $composerJson, array $phpCoreExtensions = []): a
                 continue;
             }
 
-            if (strpos($require, 'ext-') !== 0) {
+            if (! str_starts_with($require, 'ext-')) {
                 continue;
             }
 
diff --git a/src/ComposerRequireChecker/DependencyGuesser/GuessFromLoadedExtensions.php b/src/ComposerRequireChecker/DependencyGuesser/GuessFromLoadedExtensions.php
index 25236e01..a401043d 100644
--- a/src/ComposerRequireChecker/DependencyGuesser/GuessFromLoadedExtensions.php
+++ b/src/ComposerRequireChecker/DependencyGuesser/GuessFromLoadedExtensions.php
@@ -41,7 +41,7 @@ public function __invoke(string $symbolName): Generator
                 continue;
             }
 
-            if ($this->coreExtensions && in_array($extensionName, $this->coreExtensions)) {
+            if ($this->coreExtensions && in_array($extensionName, $this->coreExtensions, true)) {
                 yield 'php';
             }