diff --git a/include/quickjs/quickjs.h b/include/quickjs/quickjs.h
index c28c48cf4..290bb8e82 100644
--- a/include/quickjs/quickjs.h
+++ b/include/quickjs/quickjs.h
@@ -503,6 +503,8 @@ typedef struct JSClassDef {
 } JSClassDef;
 
 JSClassID JS_NewClassID(JSClassID *pclass_id);
+JSClassID JS_GetClassID(JSValueConst v);
+
 int JS_NewClass(JSRuntime *rt, JSClassID class_id, const JSClassDef *class_def);
 int JS_IsRegisteredClass(JSRuntime *rt, JSClassID class_id);
 
@@ -795,6 +797,7 @@ JSValue JS_NewPromiseCapability(JSContext *ctx, JSValue *resolving_funcs);
 /* is_handled = TRUE means that the rejection is handled */
 typedef void JSHostPromiseRejectionTracker(JSContext* ctx, JSValueConst promise, JSValueConst reason, JS_BOOL is_handled, void* opaque);
 void JS_SetHostPromiseRejectionTracker(JSRuntime *rt, JSHostPromiseRejectionTracker *cb, void *opaque);
+void JS_SetHostUnhandledPromiseRejectionTracker(JSRuntime *rt, JSHostPromiseRejectionTracker *cb, void *opaque);
 
 /* return != 0 if the JS code needs to be interrupted */
 typedef int JSInterruptHandler(JSRuntime *rt, void *opaque);
diff --git a/src/core/builtins/js-promise.c b/src/core/builtins/js-promise.c
index 324530ecc..a0b001d20 100644
--- a/src/core/builtins/js-promise.c
+++ b/src/core/builtins/js-promise.c
@@ -131,6 +131,14 @@ void JS_SetHostPromiseRejectionTracker(JSRuntime *rt,
   rt->host_promise_rejection_tracker_opaque = opaque;
 }
 
+void JS_SetHostUnhandledPromiseRejectionTracker(JSRuntime *rt,
+                                       JSHostPromiseRejectionTracker *cb,
+                                       void *opaque)
+{
+  rt->host_unhandled_promise_rejection_tracker = cb;
+  rt->host_unhandled_promise_rejection_tracker_opaque = opaque;
+}
+
 void fulfill_or_reject_promise(JSContext *ctx, JSValueConst promise,
                                       JSValueConst value, BOOL is_reject)
 {
@@ -335,6 +343,14 @@ void js_promise_finalizer(JSRuntime *rt, JSValue val)
 
   if (!s)
     return;
+
+  if (s->promise_state == JS_PROMISE_REJECTED && !s->is_handled) {
+    if (rt->host_unhandled_promise_rejection_tracker) {
+      rt->host_unhandled_promise_rejection_tracker(rt, val, s->promise_result, FALSE,
+          rt->host_unhandled_promise_rejection_tracker_opaque);
+    }
+  }
+
   for(i = 0; i < 2; i++) {
     list_for_each_safe(el, el1, &s->promise_reactions[i]) {
       JSPromiseReactionData *rd =
diff --git a/src/core/runtime.c b/src/core/runtime.c
index a6f99f4b5..ff83c3f13 100644
--- a/src/core/runtime.c
+++ b/src/core/runtime.c
@@ -230,6 +230,16 @@ JSClassID JS_NewClassID(JSClassID* pclass_id) {
   return class_id;
 }
 
+JSClassID JS_GetClassID(JSValueConst v) {
+  JSObject *p;
+
+  if (JS_VALUE_GET_TAG(v) != JS_TAG_OBJECT)
+    return 0;
+  p = JS_VALUE_GET_OBJ(v);
+  assert(p != 0);
+  return p->class_id;
+}
+
 BOOL JS_IsRegisteredClass(JSRuntime* rt, JSClassID class_id) {
   return (class_id < rt->class_count && rt->class_array[class_id].class_id != 0);
 }
diff --git a/src/core/types.h b/src/core/types.h
index 1532d39f7..af18a2abc 100644
--- a/src/core/types.h
+++ b/src/core/types.h
@@ -209,6 +209,9 @@ struct JSRuntime {
     JSHostPromiseRejectionTracker *host_promise_rejection_tracker;
     void *host_promise_rejection_tracker_opaque;
 
+    JSHostPromiseRejectionTracker *host_unhandled_promise_rejection_tracker;
+    void *host_unhandled_promise_rejection_tracker_opaque;
+
     struct list_head job_list; /* list of JSJobEntry.link */
 
     JSModuleNormalizeFunc *module_normalize_func;