1 files changed, 3 insertions, 3 deletions

diff --git a/tmk_core/common/chibios/printf.h b/tmk_core/common/chibios/printf.h
index 2cdf55ed9..775459e1e 100644
--- a/tmk_core/common/chibios/printf.h
+++ b/tmk_core/common/chibios/printf.h
@@ -99,10 +99,10 @@ regs Kusti, 23.10.2004
 
 void init_printf(void* putp, void (*putf)(void*, char));
 
-void tfp_printf(char* fmt, ...);
-void tfp_sprintf(char* s, char* fmt, ...);
+int tfp_printf(const char* fmt, ...);
+int tfp_sprintf(char* s, const char* fmt, ...);
 
-void tfp_format(void* putp, void (*putf)(void*, char), char* fmt, va_list va);
+void tfp_format(void* putp, void (*putf)(void*, char), const char* fmt, va_list va);
 
 #define printf tfp_printf
 #define sprintf tfp_sprintf