diff --git a/app/code/core/Mage/Adminhtml/Block/Widget/Grid/Column/Renderer/Abstract.php b/app/code/core/Mage/Adminhtml/Block/Widget/Grid/Column/Renderer/Abstract.php
index 436131036c8..968b6402a3d 100644
--- a/app/code/core/Mage/Adminhtml/Block/Widget/Grid/Column/Renderer/Abstract.php
+++ b/app/code/core/Mage/Adminhtml/Block/Widget/Grid/Column/Renderer/Abstract.php
@@ -128,7 +128,7 @@ public function renderHeader()
. '" class="' . $className . '">'
. $this->escapeHtml($this->getColumn()->getHeader()) . '';
} else {
- $out = $this->escapeHtml($this->getColumn()->getHeader());
+ $out = '' . $this->escapeHtml($this->getColumn()->getHeader()) . '';
}
return $out;
}