diff --git a/quickjs.c b/quickjs.c
index 39fc93dca..6a2a9f1d6 100644
--- a/quickjs.c
+++ b/quickjs.c
@@ -49057,6 +49057,45 @@ static JSValue js_map_get(JSContext *ctx, JSValueConst this_val,
         return js_dup(mr->value);
 }
 
+static JSValue js_map_getOrInsert(JSContext *ctx, JSValueConst this_val,
+                                  int argc, JSValueConst *argv, int magic)
+{
+    bool computed = magic & 1;
+    JSClassID class_id = magic >> 1;
+    JSMapState *s = JS_GetOpaque2(ctx, this_val, class_id);
+    JSMapRecord *mr;
+    JSValueConst key;
+    JSValue value;
+
+    if (!s)
+        return JS_EXCEPTION;
+    if (computed && !JS_IsFunction(ctx, argv[1]))
+        return JS_ThrowTypeError(ctx, "not a function");
+    key = map_normalize_key_const(ctx, argv[0]);
+    if (s->is_weak && !is_valid_weakref_target(key))
+        return JS_ThrowTypeError(ctx, "invalid value used as WeakMap key");
+    mr = map_find_record(ctx, s, key);
+    if (!mr) {
+        if (computed) {
+            value = JS_Call(ctx, argv[1], JS_UNDEFINED, 1, &key);
+            if (JS_IsException(value))
+                return JS_EXCEPTION;
+            mr = map_find_record(ctx, s, key);
+            if (mr)
+                map_delete_record(ctx->rt, s, mr);
+        } else {
+            value = js_dup(argv[1]);
+        }
+        mr = map_add_record(ctx, s, key);
+        if (!mr) {
+            JS_FreeValue(ctx, value);
+            return JS_EXCEPTION;
+        }
+        mr->value = value;
+    }
+    return js_dup(mr->value);
+}
+
 static JSValue js_map_has(JSContext *ctx, JSValueConst this_val,
                           int argc, JSValueConst *argv, int magic)
 {
@@ -50115,6 +50154,10 @@ static const JSCFunctionListEntry js_set_funcs[] = {
 static const JSCFunctionListEntry js_map_proto_funcs[] = {
     JS_CFUNC_MAGIC_DEF("set", 2, js_map_set, 0 ),
     JS_CFUNC_MAGIC_DEF("get", 1, js_map_get, 0 ),
+    JS_CFUNC_MAGIC_DEF("getOrInsert", 2, js_map_getOrInsert,
+                       JS_CLASS_MAP<<1 | /*computed*/false ),
+    JS_CFUNC_MAGIC_DEF("getOrInsertComputed", 2, js_map_getOrInsert,
+                       JS_CLASS_MAP<<1 | /*computed*/true ),
     JS_CFUNC_MAGIC_DEF("has", 1, js_map_has, 0 ),
     JS_CFUNC_MAGIC_DEF("delete", 1, js_map_delete, 0 ),
     JS_CFUNC_MAGIC_DEF("clear", 0, js_map_clear, 0 ),
@@ -50161,6 +50204,10 @@ static const JSCFunctionListEntry js_set_iterator_proto_funcs[] = {
 static const JSCFunctionListEntry js_weak_map_proto_funcs[] = {
     JS_CFUNC_MAGIC_DEF("set", 2, js_map_set, MAGIC_WEAK ),
     JS_CFUNC_MAGIC_DEF("get", 1, js_map_get, MAGIC_WEAK ),
+    JS_CFUNC_MAGIC_DEF("getOrInsert", 2, js_map_getOrInsert,
+                       JS_CLASS_WEAKMAP<<1 | /*computed*/false ),
+    JS_CFUNC_MAGIC_DEF("getOrInsertComputed", 2, js_map_getOrInsert,
+                       JS_CLASS_WEAKMAP<<1 | /*computed*/true ),
     JS_CFUNC_MAGIC_DEF("has", 1, js_map_has, MAGIC_WEAK ),
     JS_CFUNC_MAGIC_DEF("delete", 1, js_map_delete, MAGIC_WEAK ),
     JS_PROP_STRING_DEF("[Symbol.toStringTag]", "WeakMap", JS_PROP_CONFIGURABLE ),
diff --git a/test262.conf b/test262.conf
index 776e6c1b0..5c7de14c9 100644
--- a/test262.conf
+++ b/test262.conf
@@ -226,7 +226,7 @@ Uint32Array
 Uint8Array
 uint8array-base64=skip
 Uint8ClampedArray
-upsert=skip
+upsert
 WeakMap
 WeakRef
 WeakSet