diff --git a/app/assets/javascripts/supplier/app/services/css-object.js.coffee b/app/assets/javascripts/supplier/app/services/css-object.js.coffee
index 6d7bd71c..f96db1fe 100644
--- a/app/assets/javascripts/supplier/app/services/css-object.js.coffee
+++ b/app/assets/javascripts/supplier/app/services/css-object.js.coffee
@@ -20,6 +20,6 @@ App.CssObject.reopenClass
 
   isColorDark: (rgb_hex)->
     return false unless rgb_hex?.match /#[0-9a-zA-Z]{6}/
-    [r, g, b] = @rgb_to_numeric(rgb_hex)
+    [r, g, b] = @rgb_to_numeric rgb_hex
     luma = 0.2126 * r + 0.7152 * g + 0.0722 * b # per ITU-R BT.709
     luma < 40