diff --git a/cores/arduino/wiring_constants.h b/cores/arduino/wiring_constants.h
index 3915c2267e619a32dc8f9c45b1d19b35c95a8559..94d6cfbafc11b184004d4ec6448e4078c12b0b81 100644
--- a/cores/arduino/wiring_constants.h
+++ b/cores/arduino/wiring_constants.h
@@ -96,9 +96,8 @@ typedef unsigned int word;
 
 #define bit(b) (1UL << (b))
 
-// TODO: to be checked
-typedef uint8_t boolean ;
-typedef uint8_t byte ;
+typedef bool boolean;
+typedef uint8_t byte;
 
 #ifdef __cplusplus
 } // extern "C"