diff --git a/rector.php b/rector.php
index 683240b21ca0..0716ef24a9b7 100644
--- a/rector.php
+++ b/rector.php
@@ -45,6 +45,7 @@
 use Rector\Set\ValueObject\LevelSetList;
 use Rector\Set\ValueObject\SetList;
 use Rector\Strict\Rector\If_\BooleanInIfConditionRuleFixerRector;
+use Rector\TypeDeclaration\Rector\StmtsAwareInterface\DeclareStrictTypesRector;
 use Utils\Rector\PassStrictParameterToFunctionParameterRector;
 use Utils\Rector\RemoveErrorSuppressInTryCatchStmtsRector;
 use Utils\Rector\RemoveVarTagFromClassConstantRector;
@@ -108,6 +109,19 @@
             __DIR__ . '/system/Session/Handlers',
         ],
 
+        DeclareStrictTypesRector::class => [
+            __DIR__ . '/app',
+            __DIR__ . '/system/CodeIgniter.php',
+            __DIR__ . '/system/Config/BaseConfig.php',
+            __DIR__ . '/system/Commands/Generators/Views',
+            __DIR__ . '/system/Pager/Views',
+            __DIR__ . '/system/Test/ControllerTestTrait.php',
+            __DIR__ . '/system/Validation/Views',
+            __DIR__ . '/system/View/Parser.php',
+            __DIR__ . '/tests/system/Debug/ExceptionsTest.php',
+            __DIR__ . '/tests/system/View/Views',
+        ],
+
         // use mt_rand instead of random_int on purpose on non-cryptographically random
         RandomFunctionRector::class,
 
@@ -118,6 +132,7 @@
     $rectorConfig->importNames();
     $rectorConfig->removeUnusedImports();
 
+    $rectorConfig->rule(DeclareStrictTypesRector::class);
     $rectorConfig->rule(UnderscoreToCamelCaseVariableNameRector::class);
     $rectorConfig->rule(SimplifyUselessVariableRector::class);
     $rectorConfig->rule(RemoveAlwaysElseRector::class);