diff --git a/helper.php b/helper.php
index 6fc2cc5..27bf579 100644
--- a/helper.php
+++ b/helper.php
@@ -666,7 +666,7 @@ function renderODTOpenTable ($renderer, $attr, $style, $attr_string) {
             $css_properties ['display'] = 'printer';
         }
 
-        $background_color = $css_properties ['background-color'];
+        $background_color = $css_properties ['background-color'] ?? null;
         $image = $css_properties ['background-image'] ?? null;
         $margin_top = $css_properties ['margin-top'];
         $margin_right = $css_properties ['margin-right'];