diff --git a/mozjs/js/src/vm/SelfHosting.cpp b/mozjs/js/src/vm/SelfHosting.cpp
index 4395c09..3cc6f73 100644
--- a/mozjs/js/src/vm/SelfHosting.cpp
+++ b/mozjs/js/src/vm/SelfHosting.cpp
@@ -875,6 +875,23 @@ intrinsic_ConstructorForTypedArray(JSContext *cx, unsigned argc, Value *vp)
     return true;
 }
 
+static bool intrinsic_CheckDOMProtochain(JSContext *cx, unsigned argc, Value *vp)
+{
+    CallArgs args = CallArgsFromVp(argc, vp);
+    MOZ_ASSERT(args.length() == 3);
+    MOZ_ASSERT(args[0].isObject());
+    MOZ_ASSERT(args[1].isInt32());
+    MOZ_ASSERT(args[2].isInt32());
+
+    RootedObject object(cx, &args[0].toObject());
+    const Class *clasp = object->getClass();
+    bool match = clasp->isDOMClass() &&
+        cx->runtime()->DOMcallbacks->instanceClassMatchesProto(
+            clasp, args[1].toInt32(), args[2].toInt32());
+    args.rval().setBoolean(match);
+    return true;
+}
+
 // The self-hosting global isn't initialized with the normal set of builtins.
 // Instead, individual C++-implemented functions that're required by
 // self-hosted code are defined as global functions. Accessing these
@@ -1071,6 +1088,8 @@ static const JSFunctionSpec intrinsic_functions[] = {
     JS_FN("regexp_test_no_statics", regexp_test_no_statics, 2,0),
     JS_FN("regexp_construct_no_statics", regexp_construct_no_statics, 2,0),
 
+    JS_FN("CheckDOMProtochain", intrinsic_CheckDOMProtochain, 3, 0),
+
     JS_FS_END
 };