diff --git a/include/lib/libc/aarch64/stdio_.h b/include/lib/libc/aarch64/stdio_.h
index ad0b200..09b0172 100644
--- a/include/lib/libc/aarch64/stdio_.h
+++ b/include/lib/libc/aarch64/stdio_.h
@@ -4,6 +4,9 @@
  * SPDX-License-Identifier: BSD-3-Clause
  */
 
+#ifndef STDIO__H
+#define STDIO__H
+
 #ifndef SIZET_
 typedef unsigned long size_t;
 #define SIZET_
@@ -13,3 +16,5 @@
 typedef long ssize_t;
 #define SSIZET_
 #endif
+
+#endif /* STDIO__H */