diff --git a/arch/renesas/include/rx65n/types.h b/arch/renesas/include/rx65n/types.h
index 19da2f281e..f01ba75871 100644
--- a/arch/renesas/include/rx65n/types.h
+++ b/arch/renesas/include/rx65n/types.h
@@ -61,6 +61,9 @@ typedef signed long long   _int64_t;
 typedef unsigned long long _uint64_t;
 #define __INT64_DEFINED
 
+typedef _int64_t           _intmax_t;
+typedef _uint64_t          _uintmax_t;
+
 /* A size is 4 bytes */
 
 #if defined(__SIZE_TYPE__)