diff --git a/toolkit/content/widgets/datetimepicker.xml b/toolkit/content/widgets/datetimepicker.xml
index 6ced8ff9b3f..c235addbf43 100644
--- a/toolkit/content/widgets/datetimepicker.xml
+++ b/toolkit/content/widgets/datetimepicker.xml
@@ -364,7 +364,7 @@
           <![CDATA[
             if (typeof val == "number")
               this.setAttribute("increment", val);
-            return increment;
+            return val;
           ]]>
         </setter>
       </property>