diff --git a/src/Symfony/Component/Console/Question/ChoiceQuestion.php b/src/Symfony/Component/Console/Question/ChoiceQuestion.php
index 72703fb16767..6247ca7162eb 100644
--- a/src/Symfony/Component/Console/Question/ChoiceQuestion.php
+++ b/src/Symfony/Component/Console/Question/ChoiceQuestion.php
@@ -131,18 +131,18 @@ private function getDefaultValidator(): callable
         return function ($selected) use ($choices, $errorMessage, $multiselect, $isAssoc) {
             if ($multiselect) {
                 // Check for a separated comma values
-                if (!preg_match('/^[^,]+(?:,[^,]+)*$/', $selected, $matches)) {
+                if (!preg_match('/^[^,]+(?:,[^,]+)*$/', (string) $selected, $matches)) {
                     throw new InvalidArgumentException(sprintf($errorMessage, $selected));
                 }
 
-                $selectedChoices = explode(',', $selected);
+                $selectedChoices = explode(',', (string) $selected);
             } else {
                 $selectedChoices = [$selected];
             }
 
             if ($this->isTrimmable()) {
                 foreach ($selectedChoices as $k => $v) {
-                    $selectedChoices[$k] = trim($v);
+                    $selectedChoices[$k] = trim((string) $v);
                 }
             }
 
diff --git a/src/Symfony/Component/Console/Tests/Question/ChoiceQuestionTest.php b/src/Symfony/Component/Console/Tests/Question/ChoiceQuestionTest.php
index 9db12f852841..327f69ad79a8 100644
--- a/src/Symfony/Component/Console/Tests/Question/ChoiceQuestionTest.php
+++ b/src/Symfony/Component/Console/Tests/Question/ChoiceQuestionTest.php
@@ -19,14 +19,15 @@ class ChoiceQuestionTest extends TestCase
     /**
      * @dataProvider selectUseCases
      */
-    public function testSelectUseCases($multiSelect, $answers, $expected, $message)
+    public function testSelectUseCases($multiSelect, $answers, $expected, $message, $default = null)
     {
         $question = new ChoiceQuestion('A question', [
             'First response',
             'Second response',
             'Third response',
             'Fourth response',
-        ]);
+            null,
+        ], $default);
 
         $question->setMultiselect($multiSelect);
 
@@ -59,6 +60,19 @@ public function selectUseCases()
                 ['First response', 'Second response'],
                 'When passed multiple answers on MultiSelect, the defaultValidator must return these answers as an array',
             ],
+            [
+                false,
+                [null],
+                null,
+                'When used null as default single answer on singleSelect, the defaultValidator must return this answer as null',
+            ],
+            [
+                false,
+                ['First response'],
+                'First response',
+                'When used a string as default single answer on singleSelect, the defaultValidator must return this answer as a string',
+                'First response',
+            ],
         ];
     }