diff --git a/src/Mutator/FunctionSignature/ProtectedVisibility.php b/src/Mutator/FunctionSignature/ProtectedVisibility.php
index 22292f1d9..807e1aa27 100644
--- a/src/Mutator/FunctionSignature/ProtectedVisibility.php
+++ b/src/Mutator/FunctionSignature/ProtectedVisibility.php
@@ -65,6 +65,11 @@ private function hasSameProtectedParentMethod(Node $node): bool
         /** @var \ReflectionClass $reflection */
         $reflection = $node->getAttribute(ReflectionVisitor::REFLECTION_CLASS_KEY);
 
+        if (!$reflection instanceof \ReflectionClass) {
+            // assuming the worst where interface has the same method
+            return true;
+        }
+
         $parent = $reflection->getParentClass();
 
         while ($parent) {
diff --git a/src/Mutator/FunctionSignature/PublicVisibility.php b/src/Mutator/FunctionSignature/PublicVisibility.php
index 6defd96ed..0e3c92aee 100644
--- a/src/Mutator/FunctionSignature/PublicVisibility.php
+++ b/src/Mutator/FunctionSignature/PublicVisibility.php
@@ -100,6 +100,11 @@ private function hasSamePublicMethodInInterface(Node $node): bool
         /** @var \ReflectionClass $reflection */
         $reflection = $node->getAttribute(ReflectionVisitor::REFLECTION_CLASS_KEY);
 
+        if (!$reflection instanceof \ReflectionClass) {
+            // assuming the worst where interface has the same method
+            return true;
+        }
+
         foreach ($reflection->getInterfaces() as $reflectionInterface) {
             try {
                 $method = $reflectionInterface->getMethod($node->name->name);
@@ -121,6 +126,11 @@ private function hasSamePublicMethodInParentClass(Node $node): bool
         /** @var \ReflectionClass $reflection */
         $reflection = $node->getAttribute(ReflectionVisitor::REFLECTION_CLASS_KEY);
 
+        if (!$reflection instanceof \ReflectionClass) {
+            // assuming the worst where interface has the same method
+            return true;
+        }
+
         $parent = $reflection->getParentClass();
 
         while ($parent) {
diff --git a/tests/Mutator/FunctionSignature/ProtectedVisibilityTest.php b/tests/Mutator/FunctionSignature/ProtectedVisibilityTest.php
index dc8f1b17a..bd3b2673e 100644
--- a/tests/Mutator/FunctionSignature/ProtectedVisibilityTest.php
+++ b/tests/Mutator/FunctionSignature/ProtectedVisibilityTest.php
@@ -179,6 +179,22 @@ private function bar()
     {
     }
 }
+PHP
+        ];
+
+        yield 'it does not mutate an anonymous class because reflection is not avalable' => [
+            <<<'PHP'
+<?php
+
+function something()
+{
+    return new class() {
+        protected function anything()
+        {
+            return null;
+        }
+    };
+}
 PHP
         ];
     }
diff --git a/tests/Mutator/FunctionSignature/PublicVisibilityTest.php b/tests/Mutator/FunctionSignature/PublicVisibilityTest.php
index d98fff3c3..ded07fc33 100644
--- a/tests/Mutator/FunctionSignature/PublicVisibilityTest.php
+++ b/tests/Mutator/FunctionSignature/PublicVisibilityTest.php
@@ -234,6 +234,22 @@ protected function bar()
     {
     }
 }
+PHP
+        ];
+
+        yield 'it does not mutate an anonymous class because reflection is not avalable' => [
+            <<<'PHP'
+<?php
+
+function something()
+{
+    return new class() {
+        public function anything()
+        {
+            return null;
+        }
+    };
+}
 PHP
         ];
     }