diff --git a/libs/Captcha/CaptchaBuilder.php b/libs/Captcha/CaptchaBuilder.php
index bbd8602eb..356da5aa0 100644
--- a/libs/Captcha/CaptchaBuilder.php
+++ b/libs/Captcha/CaptchaBuilder.php
@@ -427,7 +427,7 @@ class CaptchaBuilder implements CaptchaBuilderInterface
                 $color = $this->backgroundColor;
                 $bg = imagecolorallocate($image, $color[0], $color[1], $color[2]);
             }
-            $this->background = $bg;
+            $this->backgroundColor = $bg;
             imagefill($image, 0, 0, $bg);
         } else {
             // use a random background image