diff --git a/src/Symfony/Component/VarDumper/Dumper/AbstractDumper.php b/src/Symfony/Component/VarDumper/Dumper/AbstractDumper.php
index ec8189b64b..4e72c1887f 100644
--- a/src/Symfony/Component/VarDumper/Dumper/AbstractDumper.php
+++ b/src/Symfony/Component/VarDumper/Dumper/AbstractDumper.php
@@ -167,6 +167,9 @@ abstract class AbstractDumper implements DataDumperInterface, DumperInterface
      */
     protected function utf8Encode($s)
     {
+        if (!function_exists('iconv')) {
+            throw new \RuntimeException('Unable to convert a non-UTF-8 string to UTF-8: required function iconv() does not exist. You should install ext-iconv or symfony/polyfill-iconv.');
+        }
         if (false !== $c = @iconv($this->charset, 'UTF-8', $s)) {
             return $c;
         }
diff --git a/src/Symfony/Component/VarDumper/composer.json b/src/Symfony/Component/VarDumper/composer.json
index 8213966c5a..5d0ca61a49 100644
--- a/src/Symfony/Component/VarDumper/composer.json
+++ b/src/Symfony/Component/VarDumper/composer.json
@@ -20,12 +20,14 @@
         "symfony/polyfill-mbstring": "~1.0"
     },
     "require-dev": {
+        "ext-iconv": "*",
         "twig/twig": "~1.20|~2.0"
     },
     "conflict": {
         "phpunit/phpunit": "<4.8.35|<5.4.3,>=5.0"
     },
     "suggest": {
+        "ext-iconv": "To convert non-UTF-8 strings to UTF-8 (or symfony/polyfill-iconv in case ext-iconv cannot be used).",
         "ext-symfony_debug": ""
     },
     "autoload": {