diff --git a/udev_list.c b/udev_list.c
index 4c00023..0696468 100644
--- a/udev_list.c
+++ b/udev_list.c
@@ -43,7 +43,7 @@ struct udev_list_entry *udev_list_entry_add(struct udev_list_entry *list_entry,
         }
 
         free(old->value);
-        old->value = strdup(value);
+        old->value = value ? strdup(value) : NULL;
         return old;
     }