diff --git a/libc/src/__support/OSUtil/fuchsia/io.h b/libc/src/__support/OSUtil/fuchsia/io.h
new file mode 100644
--- /dev/null
+++ b/libc/src/__support/OSUtil/fuchsia/io.h
@@ -0,0 +1,28 @@
+//===------------- Fuchsia implementation of IO utils -----------*- C++ -*-===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_LIBC_SRC_SUPPORT_OSUTIL_FUCHSIA_IO_H
+#define LLVM_LIBC_SRC_SUPPORT_OSUTIL_FUCHSIA_IO_H
+
+#ifndef LIBC_COPT_TEST_USE_FUCHSIA
+#error this file should only be used by tests
+#endif
+
+#include "src/__support/CPP/string_view.h"
+
+#include <zircon/sanitizer.h>
+
+namespace __llvm_libc {
+
+LIBC_INLINE void write_to_stderr(cpp::string_view msg) {
+  __sanitizer_log_write(msg.data(), msg.size());
+}
+
+} // namespace __llvm_libc
+
+#endif // LLVM_LIBC_SRC_SUPPORT_OSUTIL_FUCHSIA_IO_H
diff --git a/libc/src/__support/OSUtil/io.h b/libc/src/__support/OSUtil/io.h
--- a/libc/src/__support/OSUtil/io.h
+++ b/libc/src/__support/OSUtil/io.h
@@ -15,6 +15,8 @@
 #include "gpu/io.h"
 #elif defined(__unix__)
 #include "linux/io.h"
+#elif defined(__Fuchsia__)
+#include "fuchsia/io.h"
 #endif
 
 #endif // LLVM_LIBC_SRC_SUPPORT_OSUTIL_IO_H