diff --git a/waterbox/libcxx/setup-llvm.sh b/waterbox/libcxx/setup-llvm.sh
index d1e9e6f331..e8b1cc6ab9 100755
--- a/waterbox/libcxx/setup-llvm.sh
+++ b/waterbox/libcxx/setup-llvm.sh
@@ -1,7 +1,7 @@
 #!/bin/sh
 set -e
 LLVM_TAG=llvmorg-18.1.3
-LLVM_DIRS="cmake compiler-rt libunwind libcxx libcxxabi"
+LLVM_DIRS="cmake compiler-rt libunwind libcxx libcxxabi runtimes"
 LLVM_PATH=../llvm-project
 LLVM_GIT_DIR=$(git rev-parse --git-path modules/waterbox/llvm-project)