1 files changed, 6 insertions, 0 deletions
diff --git a/quickjs.c b/quickjs.c
index 4c4d273..58c638a 100644
--- a/quickjs.c
+++ b/quickjs.c
@@ -7336,6 +7336,12 @@ static int JS_AddBrand(JSContext *ctx, JSValueConst obj, JSValueConst home_obj)
         return -1;
     }
     p1 = JS_VALUE_GET_OBJ(obj);
+    prs = find_own_property(&pr, p1, brand_atom);
+    if (unlikely(prs)) {
+        JS_FreeAtom(ctx, brand_atom);
+        JS_ThrowTypeError(ctx, "private method is already present");
+        return -1;
+    }
     pr = add_property(ctx, p1, brand_atom, JS_PROP_C_W_E);
     JS_FreeAtom(ctx, brand_atom);
     if (!pr)