diff --git a/pkgs/development/compilers/llvm/common/llvm/default.nix b/pkgs/development/compilers/llvm/common/llvm/default.nix
index 345e466412c2..42825922d7de 100644
--- a/pkgs/development/compilers/llvm/common/llvm/default.nix
+++ b/pkgs/development/compilers/llvm/common/llvm/default.nix
@@ -93,6 +93,8 @@ let
     '' + lib.optionalString enablePolly ''
       chmod u+w "$out/${pname}/tools"
       cp -r ${monorepoSrc}/polly "$out/${pname}/tools"
+    '' + lib.optionalString (lib.versionAtLeast release_version "21") ''
+      cp -r ${monorepoSrc}/libc "$out"
     '') else src;
 in
 
diff --git a/pkgs/development/compilers/llvm/default.nix b/pkgs/development/compilers/llvm/default.nix
index 30825787132a..8aa6891e0f83 100644
--- a/pkgs/development/compilers/llvm/default.nix
+++ b/pkgs/development/compilers/llvm/default.nix
@@ -33,9 +33,9 @@ let
     "19.1.7".officialRelease.sha256 = "sha256-cZAB5vZjeTsXt9QHbP5xluWNQnAHByHtHnAhVDV0E6I=";
     "20.1.1".officialRelease.sha256 = "sha256-hDFYi5wAUDQ8xfjvbGFi05KdawrN9lwrrSC8AcTpCEE=";
     "21.0.0-git".gitRelease = {
-      rev = "4fde8c341f9166e6ec6dff6e7704be175e382f5b";
-      rev-version = "21.0.0-unstable-2025-03-16";
-      sha256 = "sha256-LOQdDYbWvPfUxaR7G3UFQlGzmwaUxHuLDOXgixKB18g=";
+      rev = "b32cf756994cbab83e50b9d84df03d5ee03f31f8";
+      rev-version = "21.0.0-unstable-2025-03-23";
+      sha256 = "sha256-6PuKOT8TozoOcN1muWt08jHGLMQTogtMOQIFa8TTQoY=";
     };
   } // llvmVersions;