diff --git a/src/gos/gos_arduino.h b/src/gos/gos_arduino.h
index 6a18aaec..3019d271 100644
--- a/src/gos/gos_arduino.h
+++ b/src/gos/gos_arduino.h
@@ -31,7 +31,7 @@
 /* Type definitions                                                          */
 /*===========================================================================*/
 
-typedef bool	bool_t;
+typedef unsigned char	bool_t;
 
 #if 0
 	// Already defined by Arduino