diff --git a/extension.json b/extension.json
index ab03d718..597934bc 100644
--- a/extension.json
+++ b/extension.json
@@ -6,7 +6,7 @@
 	"license-name": "GPL-2.0-or-later",
 	"type": "parserhook",
 	"requires": {
-		"MediaWiki": ">= 1.42"
+		"MediaWiki": ">= 1.43"
 	},
 	"SpecialPages": {
 		"CategoryTree": {
diff --git a/includes/ApiCategoryTree.php b/includes/ApiCategoryTree.php
index 04446d5f..8b794e28 100644
--- a/includes/ApiCategoryTree.php
+++ b/includes/ApiCategoryTree.php
@@ -4,7 +4,7 @@ namespace MediaWiki\Extension\CategoryTree;
 
 use ApiBase;
 use ApiMain;
-use FormatJson;
+use MediaWiki\Json\FormatJson;
 use MediaWiki\Languages\LanguageConverterFactory;
 use MediaWiki\Linker\LinkRenderer;
 use MediaWiki\MainConfigNames;
diff --git a/includes/OptionManager.php b/includes/OptionManager.php
index 1bea88db..7416e23c 100644
--- a/includes/OptionManager.php
+++ b/includes/OptionManager.php
@@ -24,9 +24,9 @@
 
 namespace MediaWiki\Extension\CategoryTree;
 
-use FormatJson;
 use InvalidArgumentException;
 use MediaWiki\Config\Config;
+use MediaWiki\Json\FormatJson;
 use MediaWiki\MediaWikiServices;
 
 /**