diff --git a/components/script_bindings/conversions.rs b/components/script_bindings/conversions.rs
index a45da5b4cc4..4d8e7aa595c 100644
--- a/components/script_bindings/conversions.rs
+++ b/components/script_bindings/conversions.rs
@@ -245,6 +245,9 @@ pub unsafe fn get_dom_class(obj: *mut JSObject) -> Result<&'static DOMClass, ()>
     if is_dom_proxy(obj) {
         trace!("proxy dom object");
         let dom_class: *const DOMClass = GetProxyHandlerExtra(obj) as *const DOMClass;
+        if dom_class.is_null() {
+            return Err(());
+        }
         return Ok(&*dom_class);
     }
     trace!("not a dom object");