diff --git a/components/script/dom/bindings/codegen/CodegenRust.py b/components/script/dom/bindings/codegen/CodegenRust.py
index 579f84301d30..21573cf4bead 100644
--- a/components/script/dom/bindings/codegen/CodegenRust.py
+++ b/components/script/dom/bindings/codegen/CodegenRust.py
@@ -398,7 +398,7 @@ def pickFirstSignature(condition, filterLambda):
                 return False
 
             # First check for null or undefined
-            pickFirstSignature("%s.isNullOrUndefined()" % distinguishingArg,
+            pickFirstSignature("%s.get().is_null_or_undefined()" % distinguishingArg,
                                lambda s: (s[1][distinguishingIndex].type.nullable() or
                                           s[1][distinguishingIndex].type.isDictionary()))