diff --git a/cpu/k60/devio/devio-null.c b/cpu/k60/devio/devio-null.c
index 8b53985ea1..26139049e3 100644
--- a/cpu/k60/devio/devio-null.c
+++ b/cpu/k60/devio/devio-null.c
@@ -25,22 +25,33 @@
 
 int  devnull_open_r(struct _reent *r, const char *path, int flags, int mode)
 {
+    (void) r;
+    (void) path;
+    (void) flags;
+    (void) mode;
     return 0;
 }
 
 int  devnull_close_r(struct _reent *r, int fd)
 {
+    (void) r;
+    (void) fd;
     return 0;
 }
 
 long devnull_write_r(struct _reent *r, int fd, const char *ptr, int len)
 {
+    (void) r;
+    (void) fd;
+    (void) ptr;
     /* Aaand... it's gone!*/
     return len;
 }
 
 long devnull_read_r(struct _reent *r, int fd, char *ptr, int len)
 {
+    (void) r;
+    (void) fd;
     /* Read null bytes */
     memset(ptr, '\0', len);
     return len;
@@ -48,12 +59,20 @@ long devnull_read_r(struct _reent *r, int fd, char *ptr, int len)
 
 long devnull_lseek_r(struct _reent *r, int fd, int ptr, int dir)
 {
+    (void) r;
+    (void) fd;
+    (void) ptr;
+    (void) dir;
     r->_errno = ENOSYS;
     return -1;
 }
 
 long devnull_fstat_r(struct _reent *r, int fd, char *ptr, int len)
 {
+    (void) r;
+    (void) fd;
+    (void) ptr;
+    (void) len;
     r->_errno = ENOSYS;
     return -1;
 }
diff --git a/cpu/k60/devio/devio-uart.c b/cpu/k60/devio/devio-uart.c
index ff44d07840..a1880e448b 100644
--- a/cpu/k60/devio/devio-uart.c
+++ b/cpu/k60/devio/devio-uart.c
@@ -26,6 +26,8 @@
 static inline long uart_write_r(uart_t uart_num, struct _reent *r, int fd, const char *ptr,
                                 int len)
 {
+    (void) r;
+    (void) fd;
     int i = 0;
 
     while (i < len) {
@@ -39,6 +41,11 @@ static inline long uart_write_r(uart_t uart_num, struct _reent *r, int fd, const
 static long uart_read_r(uart_t uart_num, struct _reent *r, int fd, char *ptr, int len)
 {
     /* not yet implemented */
+    (void) uart_num;
+    (void) r;
+    (void) fd;
+    (void) ptr;
+    (void) len;
     return 0;
 }
 
diff --git a/cpu/k60/syscalls.c b/cpu/k60/syscalls.c
index 94ad9ca96b..b7ab93f48c 100644
--- a/cpu/k60/syscalls.c
+++ b/cpu/k60/syscalls.c
@@ -67,19 +67,17 @@ static ringbuffer_t rx_buf;
  */
 static void stdio_rx_cb(void *arg, char data)
 {
-#ifndef MODULE_UART0
     (void)arg;
 
-    ringbuffer_add_one(&rx_buf, data);
-    mutex_unlock(&uart_rx_mutex);
-#else
-
+#ifdef MODULE_UART0
     if (uart0_handler_pid) {
         uart0_handle_incoming(data);
 
         uart0_notify_thread();
     }
-
+#else
+    ringbuffer_add_one(&rx_buf, data);
+    mutex_unlock(&uart_rx_mutex);
 #endif
 }
 
@@ -119,6 +117,7 @@ _exit(int code)
     /* See local variable `status` during debugger break. */
     asm volatile ("bkpt #0");
 #else
+    (void) code;
     NVIC_SystemReset();
 #endif