diff --git a/libcxx/include/__utility/unreachable.h b/libcxx/include/__utility/unreachable.h
--- a/libcxx/include/__utility/unreachable.h
+++ b/libcxx/include/__utility/unreachable.h
@@ -9,8 +9,8 @@
 #ifndef _LIBCPP___UTILITY_UNREACHABLE_H
 #define _LIBCPP___UTILITY_UNREACHABLE_H
 
+#include <__assert>
 #include <__config>
-#include <cstdlib>
 
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
 #  pragma GCC system_header
@@ -18,21 +18,17 @@
 
 _LIBCPP_BEGIN_NAMESPACE_STD
 
-_LIBCPP_NORETURN _LIBCPP_HIDE_FROM_ABI inline void __libcpp_unreachable()
-{
-#if __has_builtin(__builtin_unreachable)
-  __builtin_unreachable();
-#else
-  std::abort();
-#endif
+_LIBCPP_NORETURN _LIBCPP_HIDE_FROM_ABI inline void __libcpp_unreachable() {
+    _LIBCPP_ASSERT(false, "std::unreachable() was reached");
+    __builtin_unreachable();
 }
 
 #if _LIBCPP_STD_VER > 20
 
 [[noreturn]] _LIBCPP_HIDE_FROM_ABI inline void unreachable() { __libcpp_unreachable(); }
 
-#endif // _LIBCPP_STD_VER > 20
+#endif
 
 _LIBCPP_END_NAMESPACE_STD
 
-#endif
+#endif // _LIBCPP___UTILITY_UNREACHABLE_H
diff --git a/libcxx/include/utility b/libcxx/include/utility
--- a/libcxx/include/utility
+++ b/libcxx/include/utility
@@ -274,6 +274,7 @@
 #endif
 
 #if !defined(_LIBCPP_REMOVE_TRANSITIVE_INCLUDES) && _LIBCPP_STD_VER <= 20
+#  include <cstdlib>
 #  include <iosfwd>
 #  include <type_traits>
 #endif
diff --git a/libcxx/test/libcxx/transitive_includes/cxx2b.csv b/libcxx/test/libcxx/transitive_includes/cxx2b.csv
--- a/libcxx/test/libcxx/transitive_includes/cxx2b.csv
+++ b/libcxx/test/libcxx/transitive_includes/cxx2b.csv
@@ -693,7 +693,6 @@
 unordered_set version
 utility compare
 utility cstddef
-utility cstdlib
 utility initializer_list
 utility limits
 utility version
diff --git a/libcxx/test/std/utilities/utility/utility.unreachable/assert.unreachable.pass.cpp b/libcxx/test/std/utilities/utility/utility.unreachable/assert.unreachable.pass.cpp
new file mode 100644
--- /dev/null
+++ b/libcxx/test/std/utilities/utility/utility.unreachable/assert.unreachable.pass.cpp
@@ -0,0 +1,25 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++03, c++11, c++14, c++17, c++20
+
+// REQUIRES: has-unix-headers
+// XFAIL: use_system_cxx_lib && target={{.+}}-apple-macosx{{10.9|10.10|10.11|10.12|10.13|10.14|10.15|11.0|12.0}}
+// ADDITIONAL_COMPILE_FLAGS: -D_LIBCPP_ENABLE_ASSERTIONS=1
+
+// Make sure that reaching std::unreachable() with assertions enabled triggers an assertion.
+
+#include <utility>
+
+#include "check_assertion.h"
+
+int main(int, char**) {
+    TEST_LIBCPP_ASSERT_FAILURE(std::unreachable(), "std::unreachable() was reached");
+
+    return 0;
+}
diff --git a/libcxx/test/std/utilities/utility/utility.unreachable/unreachable.compile.pass.cpp b/libcxx/test/std/utilities/utility/utility.unreachable/unreachable.pass.cpp
rename from libcxx/test/std/utilities/utility/utility.unreachable/unreachable.compile.pass.cpp
rename to libcxx/test/std/utilities/utility/utility.unreachable/unreachable.pass.cpp
--- a/libcxx/test/std/utilities/utility/utility.unreachable/unreachable.compile.pass.cpp
+++ b/libcxx/test/std/utilities/utility/utility.unreachable/unreachable.pass.cpp
@@ -8,7 +8,20 @@
 
 // UNSUPPORTED: c++03, c++11, c++14, c++17, c++20
 
-#include <utility>
+// Make sure we can use `std::unreachable()`. We can't actually execute it cause that would be
+// UB, but we can make sure that it doesn't cause a linker error or something like that.
+
+#include <cassert>
 #include <type_traits>
+#include <utility>
+
+int main(int argc, char**) {
+    assert(argc == 1);
+    if (argc != 1) {
+        std::unreachable();
+    }
+
+    static_assert(std::is_same_v<decltype(std::unreachable()), void>);
 
-static_assert(std::is_same_v<decltype(std::unreachable()), void>);
+    return 0;
+}