diff --git a/src/Symfony/Component/Console/Helper/QuestionHelper.php b/src/Symfony/Component/Console/Helper/QuestionHelper.php
index af4d0b9cca459..7c910781b3321 100644
--- a/src/Symfony/Component/Console/Helper/QuestionHelper.php
+++ b/src/Symfony/Component/Console/Helper/QuestionHelper.php
@@ -264,7 +264,7 @@ private function autocomplete(OutputInterface $output, Question $question, $inpu
             } elseif ("\177" === $c) { // Backspace Character
                 if (0 === $numMatches && 0 !== $i) {
                     --$i;
-                    $fullChoice = substr($fullChoice, 0, -1);
+                    $fullChoice = mb_substr($fullChoice, 0, -1);
                     // Move cursor backwards
                     $output->write("\033[1D");
                 }
@@ -278,7 +278,7 @@ private function autocomplete(OutputInterface $output, Question $question, $inpu
                 }
 
                 // Pop the last character off the end of our string
-                $ret = substr($ret, 0, $i);
+                $ret = mb_substr($ret, 0, $i);
             } elseif ("\033" === $c) {
                 // Did we read an escape sequence?
                 $c .= fread($inputStream, 2);
@@ -304,7 +304,7 @@ private function autocomplete(OutputInterface $output, Question $question, $inpu
                         $remainingCharacters = substr($ret, \strlen(trim($this->mostRecentlyEnteredValue($fullChoice))));
                         $output->write($remainingCharacters);
                         $fullChoice .= $remainingCharacters;
-                        $i = \strlen($fullChoice);
+                        $i = mb_strlen($fullChoice);
                     }
 
                     if ("\n" === $c) {