diff --git a/src/aphront/configuration/AphrontApplicationConfiguration.php b/src/aphront/configuration/AphrontApplicationConfiguration.php
--- a/src/aphront/configuration/AphrontApplicationConfiguration.php
+++ b/src/aphront/configuration/AphrontApplicationConfiguration.php
@@ -303,18 +303,7 @@
       phlog($unexpected_output);
 
       if ($response instanceof AphrontWebpageResponse) {
-        echo phutil_tag(
-          'div',
-          array(
-            'style' =>
-              'background: #eeddff;'.
-              'white-space: pre-wrap;'.
-              'z-index: 200000;'.
-              'position: relative;'.
-              'padding: 8px;'.
-              'font-family: monospace',
-          ),
-          $unexpected_output);
+        $response->setUnexpectedOutput($unexpected_output);
       }
     }
 
diff --git a/src/aphront/response/AphrontWebpageResponse.php b/src/aphront/response/AphrontWebpageResponse.php
--- a/src/aphront/response/AphrontWebpageResponse.php
+++ b/src/aphront/response/AphrontWebpageResponse.php
@@ -3,14 +3,46 @@
 final class AphrontWebpageResponse extends AphrontHTMLResponse {
 
   private $content;
+  private $unexpectedOutput;
 
   public function setContent($content) {
     $this->content = $content;
     return $this;
   }
 
+  public function setUnexpectedOutput($unexpected_output) {
+    $this->unexpectedOutput = $unexpected_output;
+    return $this;
+  }
+
+  public function getUnexpectedOutput() {
+    return $this->unexpectedOutput;
+  }
+
   public function buildResponseString() {
-    return hsprintf('%s', $this->content);
+    $unexpected_output = $this->getUnexpectedOutput();
+    if (strlen($unexpected_output)) {
+      $style = array(
+        'background: linear-gradient(180deg, #eeddff, #ddbbff);',
+        'white-space: pre-wrap;',
+        'z-index: 200000;',
+        'position: relative;',
+        'padding: 16px;',
+        'font-family: monospace;',
+        'text-shadow: 1px 1px 1px white;',
+      );
+
+      $unexpected_header = phutil_tag(
+        'div',
+        array(
+          'style' => implode(' ', $style),
+        ),
+        $unexpected_output);
+    } else {
+      $unexpected_header = '';
+    }
+
+    return hsprintf('%s%s', $unexpected_header, $this->content);
   }
 
 }