diff --git a/libcxx/utils/ci/run-buildbot b/libcxx/utils/ci/run-buildbot
index 1042b110f2bf..17cb85b886ac 100755
--- a/libcxx/utils/ci/run-buildbot
+++ b/libcxx/utils/ci/run-buildbot
@@ -9,6 +9,9 @@
 
 set -ex
 set -o pipefail
+unset LANG
+unset LC_ALL
+unset LC_COLLATE
 
 PROGNAME="$(basename "${0}")"
 
@@ -146,6 +149,7 @@ check-generated-output)
     # Check if the diffs are empty, fail otherwise.
     ! grep -q '^--- a' ${BUILD_DIR}/generated_output.patch || false
     # Reject patches that introduce non-ASCII characters or hard tabs.
+    # Depends on LC_COLLATE set at the top of this script.
     ! grep -rn '[^ -~]' libcxx/include/ || false
     # Check that no dependency cycles have been introduced.
     python3 libcxx/utils/graph_header_deps.py >/dev/null