diff --git a/.appveyor.yml b/.appveyor.yml
deleted file mode 100644
index dcf64b2..0000000
--- a/.appveyor.yml
+++ /dev/null
@@ -1,92 +0,0 @@
-# Copyright 2016, 2017 Peter Dimov
-# Copyright 2017 - 2019 James E. King III
-# Copyright 2019 - 2021 Alexander Grund
-# Distributed under the Boost Software License, Version 1.0.
-# (See accompanying file LICENSE_1_0.txt or copy at http://boost.org/LICENSE_1_0.txt)
-
-#
-# Generic Appveyor build script for boostorg repositories
-# See: https://github.com/boostorg/boost-ci/
-#
-# Instructions for customizing this script for your library:
-#
-# 1. Customize the compilers and language levels you want.
-# 2. If you have more than include/, src/, test/, example/, examples/,
-#    benchmark/ or tools/ directories, set the environment variable DEPINST.
-#    For example if your build uses code in "bench/" and "fog/" directories:
-#      - DEPINST: --include bench --include fog
-# 3. Enable pull request builds in your boostorg/<library> account.
-#
-# That's it - the script will do everything else for you.
-#
-
-version: 1.0.{build}-{branch}
-
-shallow_clone: true
-
-branches:
-  only:
-    - master
-    - develop
-    - /bugfix\/.*/
-    - /feature\/.*/
-    - /fix\/.*/
-    - /pr\/.*/
-
-skip_commits:
-  files:
-    - LICENSE
-    - meta/*
-    - README.md
-
-matrix:
-  fast_finish: false
-  # Adding MAYFAIL to any matrix job allows it to fail but the build stays green:
-  allow_failures:
-    - MAYFAIL: true
-
-environment:
-  global:
-    B2_CI_VERSION: 1
-    GIT_FETCH_JOBS: 4
-    # see: http://www.boost.org/build/doc/html/bbv2/overview/invocation.html#bbv2.overview.invocation.properties
-    # to use the default for a given environment, comment it out; recommend you build debug and release however:
-    # on Windows it is important to exercise all the possibilities, especially shared vs static, however most
-    # libraries that care about this exercise it in their Jamfiles...
-    B2_ADDRESS_MODEL: 32,64
-    B2_LINK: shared,static
-    # B2_THREADING: threading=multi,single
-    B2_VARIANT: release
-
-  matrix:
-    - FLAVOR: Visual Studio 2017 C++2a Strict
-      APPVEYOR_BUILD_WORKER_IMAGE: Visual Studio 2017
-      B2_CXXFLAGS: -permissive-
-      B2_CXXSTD: 2a
-      B2_TOOLSET: msvc-14.1
-
-    - FLAVOR: cygwin (32-bit)
-      APPVEYOR_BUILD_WORKER_IMAGE: Visual Studio 2017
-      ADDPATH: C:\cygwin\bin;
-      B2_ADDRESS_MODEL: 32
-      B2_CXXSTD: 11
-      B2_TOOLSET: gcc
-
-    - FLAVOR: cygwin (64-bit)
-      APPVEYOR_BUILD_WORKER_IMAGE: Visual Studio 2017
-      ADDPATH: C:\cygwin64\bin;
-      B2_ADDRESS_MODEL: 64
-      B2_CXXSTD: 11
-      B2_TOOLSET: gcc
-
-install:
-  - git clone --depth 1 https://github.com/boostorg/boost-ci.git C:\boost-ci-cloned
-  # Copy ci folder if not testing Boost.CI
-  - if NOT "%APPVEYOR_PROJECT_NAME%" == "boost-ci" xcopy /s /e /q /i /y C:\boost-ci-cloned\ci .\ci
-  - rmdir /s /q C:\boost-ci-cloned
-  - ci\appveyor\install.bat
-
-build: off
-
-test_script: ci\build.bat
-
diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 19a344d..64712cf 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -92,8 +92,9 @@ jobs:
           - { name: Clang w/ sanitizers, sanitize: yes,
               compiler: clang-12,  cxxstd: '11,20',       os: ubuntu-latest, container: 'ubuntu:20.04', stdlib: libc++, install: 'clang-12 libc++-12-dev libc++abi-12-dev' }
 
-          - { name: MacOS w/ clang and sanitizers,
-              compiler: clang,     cxxstd: '11',          os: macos-13, sanitize: yes }
+          # https://github.com/boostorg/contract/issues/38
+          # - { name: MacOS w/ clang and sanitizers,
+          #     compiler: clang,     cxxstd: '11',          os: macos-13, sanitize: yes }
           - { compiler: clang,     cxxstd: '11,20',       os: macos-14 }
           - { compiler: clang,     cxxstd: '11,2b',       os: macos-15 }