diff --git a/src/Mutator/FunctionSignature/PublicVisibility.php b/src/Mutator/FunctionSignature/PublicVisibility.php
index bcd398005..df7c09a33 100644
--- a/src/Mutator/FunctionSignature/PublicVisibility.php
+++ b/src/Mutator/FunctionSignature/PublicVisibility.php
@@ -35,7 +35,6 @@
 
 namespace Infection\Mutator\FunctionSignature;
 
-use Infection\Mutator\Util\InterfaceParentTrait;
 use Infection\Mutator\Util\Mutator;
 use Infection\Visitor\ReflectionVisitor;
 use PhpParser\Node;
@@ -47,8 +46,6 @@
  */
 final class PublicVisibility extends Mutator
 {
-    use InterfaceParentTrait;
-
     /**
      * Replaces "public function..." with "protected function ..."
      *
@@ -81,18 +78,10 @@ protected function mutatesNode(Node $node): bool
             return false;
         }
 
-        if ($node->isAbstract()) {
-            return false;
-        }
-
         if ($node->isMagic()) {
             return false;
         }
 
-        if ($this->isBelongsToInterface($node)) {
-            return false;
-        }
-
         return !$this->hasSamePublicParentMethod($node);
     }
 
diff --git a/src/Mutator/Util/InterfaceParentTrait.php b/src/Mutator/Util/InterfaceParentTrait.php
deleted file mode 100644
index 94cb9ca1b..000000000
--- a/src/Mutator/Util/InterfaceParentTrait.php
+++ /dev/null
@@ -1,64 +0,0 @@
-<?php
-/**
- * This code is licensed under the BSD 3-Clause License.
- *
- * Copyright (c) 2017-2019, Maks Rafalko
- * All rights reserved.
- *
- * Redistribution and use in source and binary forms, with or without
- * modification, are permitted provided that the following conditions are met:
- *
- * * Redistributions of source code must retain the above copyright notice, this
- *   list of conditions and the following disclaimer.
- *
- * * Redistributions in binary form must reproduce the above copyright notice,
- *   this list of conditions and the following disclaimer in the documentation
- *   and/or other materials provided with the distribution.
- *
- * * Neither the name of the copyright holder nor the names of its
- *   contributors may be used to endorse or promote products derived from
- *   this software without specific prior written permission.
- *
- * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
- * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
- * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
- * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
- * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
- * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
- * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
- * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
- * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
- * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
- */
-
-declare(strict_types=1);
-
-namespace Infection\Mutator\Util;
-
-use Infection\Visitor\ParentConnectorVisitor;
-use PhpParser\Node;
-
-/**
- * Checks if given node belongs to Interface
- *
- * @internal
- *
- * @author Volodimir Melko <v.melko28@gmail.com>
- */
-trait InterfaceParentTrait
-{
-    private function isBelongsToInterface(Node $node): bool
-    {
-        $parentNode = $node->getAttribute(ParentConnectorVisitor::PARENT_KEY);
-
-        if ($parentNode instanceof Node\Stmt\Interface_) {
-            return true;
-        }
-
-        if ($parentNode instanceof Node) {
-            return $this->isBelongsToInterface($parentNode);
-        }
-
-        return false;
-    }
-}
diff --git a/tests/Mutator/AbstractMutatorTestCase.php b/tests/Mutator/AbstractMutatorTestCase.php
index 0510faf69..4b53fb02a 100644
--- a/tests/Mutator/AbstractMutatorTestCase.php
+++ b/tests/Mutator/AbstractMutatorTestCase.php
@@ -42,6 +42,7 @@
 use Infection\Tests\Fixtures\SimpleMutatorVisitor;
 use Infection\Visitor\CloneVisitor;
 use Infection\Visitor\FullyQualifiedClassNameVisitor;
+use Infection\Visitor\NotMutableIgnoreVisitor;
 use Infection\Visitor\ParentConnectorVisitor;
 use Infection\Visitor\ReflectionVisitor;
 use PhpParser\Lexer;
@@ -152,6 +153,7 @@ private function getMutationsFromCode(string $code, Parser $parser, array $setti
 
         $mutationsCollectorVisitor = new SimpleMutationsCollectorVisitor($this->getMutator($settings), $initialStatements);
 
+        $traverser->addVisitor(new NotMutableIgnoreVisitor());
         $traverser->addVisitor($mutationsCollectorVisitor);
         $traverser->addVisitor(new ParentConnectorVisitor());
         $traverser->addVisitor(new FullyQualifiedClassNameVisitor());