diff --git a/composer.json b/composer.json
index c1fe6b5..62f26fd 100644
--- a/composer.json
+++ b/composer.json
@@ -27,7 +27,8 @@
         }
     },
     "require": {
-        "php": "^7.2"
+        "php": "^7.2",
+        "ext-json": "*"
     },
     "require-dev": {
         "phpunit/phpunit": "^7 || ^8.2"
diff --git a/composer.lock b/composer.lock
index b92db2e..15d483e 100644
--- a/composer.lock
+++ b/composer.lock
@@ -1,10 +1,10 @@
 {
     "_readme": [
         "This file locks the dependencies of your project to a known state",
-        "Read more about it at https://getcomposer.org/doc/01-basic-usage.md#installing-dependencies",
+        "Read more about it at https://getcomposer.org/doc/01-basic-usage.md#composer-lock-the-lock-file",
         "This file is @generated automatically"
     ],
-    "content-hash": "90b4e0748d52da8937bfc59cd813c7a1",
+    "content-hash": "254824a6ce1c0ed5b1df7e76f6c98c05",
     "packages": [],
     "packages-dev": [
         {
@@ -1531,7 +1531,8 @@
     "prefer-stable": false,
     "prefer-lowest": false,
     "platform": {
-        "php": "^7.2"
+        "php": "^7.2",
+        "ext-json": "*"
     },
     "platform-dev": []
 }