diff --git a/src/Symfony/Component/DependencyInjection/Dumper/GraphvizDumper.php b/src/Symfony/Component/DependencyInjection/Dumper/GraphvizDumper.php
index f06e6e80d5..0591e024f5 100644
--- a/src/Symfony/Component/DependencyInjection/Dumper/GraphvizDumper.php
+++ b/src/Symfony/Component/DependencyInjection/Dumper/GraphvizDumper.php
@@ -32,10 +32,11 @@ class GraphvizDumper extends Dumper
 {
     private $nodes;
     private $edges;
+    // All values should be strings
     private $options = [
             'graph' => ['ratio' => 'compress'],
-            'node' => ['fontsize' => 11, 'fontname' => 'Arial', 'shape' => 'record'],
-            'edge' => ['fontsize' => 9, 'fontname' => 'Arial', 'color' => 'grey', 'arrowhead' => 'open', 'arrowsize' => 0.5],
+            'node' => ['fontsize' => '11', 'fontname' => 'Arial', 'shape' => 'record'],
+            'edge' => ['fontsize' => '9', 'fontname' => 'Arial', 'color' => 'grey', 'arrowhead' => 'open', 'arrowsize' => '0.5'],
             'node.instance' => ['fillcolor' => '#9999ff', 'style' => 'filled'],
             'node.definition' => ['fillcolor' => '#eeeeee'],
             'node.missing' => ['fillcolor' => '#ff9999', 'style' => 'filled'],
diff --git a/src/Symfony/Component/Workflow/Dumper/GraphvizDumper.php b/src/Symfony/Component/Workflow/Dumper/GraphvizDumper.php
index c3d673fa91..0f6cb33082 100644
--- a/src/Symfony/Component/Workflow/Dumper/GraphvizDumper.php
+++ b/src/Symfony/Component/Workflow/Dumper/GraphvizDumper.php
@@ -26,10 +26,11 @@ use Symfony\Component\Workflow\Marking;
  */
 class GraphvizDumper implements DumperInterface
 {
+    // All values should be strings
     protected static $defaultOptions = [
         'graph' => ['ratio' => 'compress', 'rankdir' => 'LR'],
-        'node' => ['fontsize' => 9, 'fontname' => 'Arial', 'color' => '#333333', 'fillcolor' => 'lightblue', 'fixedsize' => true, 'width' => 1],
-        'edge' => ['fontsize' => 9, 'fontname' => 'Arial', 'color' => '#333333', 'arrowhead' => 'normal', 'arrowsize' => 0.5],
+        'node' => ['fontsize' => '9', 'fontname' => 'Arial', 'color' => '#333333', 'fillcolor' => 'lightblue', 'fixedsize' => '1', 'width' => '1'],
+        'edge' => ['fontsize' => '9', 'fontname' => 'Arial', 'color' => '#333333', 'arrowhead' => 'normal', 'arrowsize' => '0.5'],
     ];
 
     /**