diff --git a/rules-tests/TypeDeclaration/Rector/ClassMethod/AddParamFromDimFetchKeyUseRector/Fixture/skip_possibly_null.php.inc b/rules-tests/TypeDeclaration/Rector/ClassMethod/AddParamFromDimFetchKeyUseRector/Fixture/skip_possibly_null.php.inc
new file mode 100644
index 00000000000..41193f6e54a
--- /dev/null
+++ b/rules-tests/TypeDeclaration/Rector/ClassMethod/AddParamFromDimFetchKeyUseRector/Fixture/skip_possibly_null.php.inc
@@ -0,0 +1,21 @@
+<?php
+
+namespace Rector\Tests\TypeDeclaration\Rector\ClassMethod\AddParamFromDimFetchKeyUseRector\Fixture;
+
+final class SkipPossiblyNull
+{
+    public function process($key)
+    {
+        if ($key === null) {
+            return;
+        }
+
+        $items = [
+            'first' => 'Firstitem',
+            111 => 'Seconditem',
+            'second' => 'Seconditem',
+        ];
+
+        return $items[$key];
+    }
+}
diff --git a/rules/TypeDeclaration/Rector/ClassMethod/AddParamFromDimFetchKeyUseRector.php b/rules/TypeDeclaration/Rector/ClassMethod/AddParamFromDimFetchKeyUseRector.php
index cb7687e482a..0d8848691a4 100644
--- a/rules/TypeDeclaration/Rector/ClassMethod/AddParamFromDimFetchKeyUseRector.php
+++ b/rules/TypeDeclaration/Rector/ClassMethod/AddParamFromDimFetchKeyUseRector.php
@@ -13,6 +13,7 @@
 use Rector\PHPStanStaticTypeMapper\Enum\TypeKind;
 use Rector\Rector\AbstractRector;
 use Rector\StaticTypeMapper\StaticTypeMapper;
+use Rector\TypeDeclaration\Guard\ParamTypeAddGuard;
 use Rector\TypeDeclarationDocblocks\NodeFinder\ArrayDimFetchFinder;
 use Rector\VendorLocker\ParentClassMethodTypeOverrideGuard;
 use Symplify\RuleDocGenerator\ValueObject\CodeSample\CodeSample;
@@ -26,7 +27,8 @@ final class AddParamFromDimFetchKeyUseRector extends AbstractRector
     public function __construct(
         private readonly ArrayDimFetchFinder $arrayDimFetchFinder,
         private readonly StaticTypeMapper $staticTypeMapper,
-        private readonly ParentClassMethodTypeOverrideGuard $parentClassMethodTypeOverrideGuard
+        private readonly ParentClassMethodTypeOverrideGuard $parentClassMethodTypeOverrideGuard,
+        private readonly ParamTypeAddGuard $paramTypeAddGuard
     ) {
     }
 
@@ -107,6 +109,10 @@ public function refactor(Node $node): ?Node
                     continue;
                 }
 
+                if (! $this->paramTypeAddGuard->isLegal($param, $classMethod)) {
+                    continue;
+                }
+
                 foreach ($dimFetches as $dimFetch) {
                     $dimFetchType = $this->getType($dimFetch->var);