diff --git a/hw/application_fpga/fw/tk1/lib.c b/hw/application_fpga/fw/tk1/lib.c
index c7c98ae..5399dbb 100644
--- a/hw/application_fpga/fw/tk1/lib.c
+++ b/hw/application_fpga/fw/tk1/lib.c
@@ -72,7 +72,7 @@ void htif_putc(char ch)
 	htif_putchar(ch);
 }
 
-void htif_lf()
+void htif_lf(void)
 {
 	htif_putchar('\n');
 }
diff --git a/hw/application_fpga/fw/tk1/lib.h b/hw/application_fpga/fw/tk1/lib.h
index 245a16d..2d3d7e3 100644
--- a/hw/application_fpga/fw/tk1/lib.h
+++ b/hw/application_fpga/fw/tk1/lib.h
@@ -8,16 +8,16 @@
 
 #include "types.h"
 
-#ifdef QEMU_CONSOLE 
+#ifdef QEMU_CONSOLE
 void htif_putc(char ch);
-void htif_lf();
+void htif_lf(void);
 void htif_puthex(uint8_t c);
 void htif_putinthex(const uint32_t n);
 void htif_puts(const char *s);
 void htif_hexdump(void *buf, int len);
 #else
 #define htif_putc(ch)
-#define htif_lf()
+#define htif_lf(void)
 #define htif_puthex(c)
 #define htif_putinthex(n)
 #define htif_puts(s)