diff --git a/include/tabby/avr/uart.h b/include/tabby/avr/uart.h
index 4bfdcbf..55c34a1 100644
--- a/include/tabby/avr/uart.h
+++ b/include/tabby/avr/uart.h
@@ -5,8 +5,8 @@
 
 void uart_init();
 
-void uart_putchar(char c, FILE *fh);
+int uart_putchar(char c, FILE *fh);
 
-char uart_getchar(FILE *fh);
+int uart_getchar(FILE *fh);
 
 #endif /* _TABBY_AVR_UART_H */