diff --git a/lake-manifest.json b/lake-manifest.json
index 3546b65..e00a7f3 100644
--- a/lake-manifest.json
+++ b/lake-manifest.json
@@ -5,7 +5,7 @@
    "type": "git",
    "subDir": null,
    "scope": "",
-   "rev": "cff8377dbe50aae42cbd04213d5b3dacf742c3ba",
+   "rev": "b09d573cbacf5a8e767292e0edeec787a81689ce",
    "name": "UnicodeBasic",
    "manifestFile": "lake-manifest.json",
    "inputRev": "main",
diff --git a/lean-toolchain b/lean-toolchain
index bd19bde..5249182 100644
--- a/lean-toolchain
+++ b/lean-toolchain
@@ -1 +1 @@
-leanprover/lean4:v4.27.0-rc1
+leanprover/lean4:v4.27.0