diff --git a/cpu/nrf51822/hwtimer_arch.c b/cpu/nrf51822/hwtimer_arch.c
index b33a095f4e..1df7928dfe 100644
--- a/cpu/nrf51822/hwtimer_arch.c
+++ b/cpu/nrf51822/hwtimer_arch.c
@@ -32,6 +32,7 @@ void (*timeout_handler)(int);
 
 void hwtimer_arch_init(void (*handler)(int), uint32_t fcpu)
 {
+    (void) fcpu;
     timeout_handler = handler;
     timer_init(HW_TIMER, 1, &irq_handler);
 }
diff --git a/cpu/nrf51822/lpm_arch.c b/cpu/nrf51822/lpm_arch.c
index d3c22a378d..64821fc56a 100644
--- a/cpu/nrf51822/lpm_arch.c
+++ b/cpu/nrf51822/lpm_arch.c
@@ -27,6 +27,7 @@ void lpm_arch_init(void)
 
 enum lpm_mode lpm_arch_set(enum lpm_mode target)
 {
+    (void) target;
     /* TODO: needs to be implemented */
     return 0;
 }
diff --git a/cpu/nrf51822/periph/rtt.c b/cpu/nrf51822/periph/rtt.c
index 4598ab0982..58fb1b65a9 100644
--- a/cpu/nrf51822/periph/rtt.c
+++ b/cpu/nrf51822/periph/rtt.c
@@ -88,6 +88,7 @@ uint32_t rtt_get_counter(void)
 
 void rtt_set_counter(uint32_t counter)
 {
+    (void) counter;
     /* not supported for the NRF51822? -> could not find out how to do this */
 }
 
diff --git a/cpu/nrf51822/syscalls.c b/cpu/nrf51822/syscalls.c
index b72403c5af..0c51de0ac3 100644
--- a/cpu/nrf51822/syscalls.c
+++ b/cpu/nrf51822/syscalls.c
@@ -156,6 +156,8 @@ int _getpid(void)
 __attribute__ ((weak))
 int _kill_r(struct _reent *r, int pid, int sig)
 {
+    (void) pid;
+    (void) sig;
     r->_errno = ESRCH;                      /* not implemented yet */
     return -1;
 }
@@ -171,6 +173,8 @@ int _kill_r(struct _reent *r, int pid, int sig)
 __attribute__ ((weak))
 int _kill(int pid, int sig)
 {
+    (void) pid;
+    (void) sig;
     errno = ESRCH;                         /* not implemented yet */
     return -1;
 }
@@ -186,6 +190,8 @@ int _kill(int pid, int sig)
  */
 int _open_r(struct _reent *r, const char *name, int mode)
 {
+    (void) name;
+    (void) mode;
     r->_errno = ENODEV;                     /* not implemented yet */
     return -1;
 }
@@ -270,6 +276,7 @@ int _write_r(struct _reent *r, int fd, const void *data, unsigned int count)
  */
 int _close_r(struct _reent *r, int fd)
 {
+    (void) fd;
     r->_errno = ENODEV;                     /* not implemented yet */
     return -1;
 }
@@ -286,6 +293,9 @@ int _close_r(struct _reent *r, int fd)
  */
 _off_t _lseek_r(struct _reent *r, int fd, _off_t pos, int dir)
 {
+    (void) fd;
+    (void) pos;
+    (void) dir;
     r->_errno = ENODEV;                     /* not implemented yet */
     return -1;
 }
@@ -301,6 +311,8 @@ _off_t _lseek_r(struct _reent *r, int fd, _off_t pos, int dir)
  */
 int _fstat_r(struct _reent *r, int fd, struct stat * st)
 {
+    (void) fd;
+    (void) st;
     r->_errno = ENODEV;                     /* not implemented yet */
     return -1;
 }
@@ -316,6 +328,8 @@ int _fstat_r(struct _reent *r, int fd, struct stat * st)
  */
 int _stat_r(struct _reent *r, char *name, struct stat *st)
 {
+    (void) name;
+    (void) st;
     r->_errno = ENODEV;                     /* not implemented yet */
     return -1;
 }
@@ -349,6 +363,7 @@ int _isatty_r(struct _reent *r, int fd)
  */
 int _unlink_r(struct _reent *r, char* path)
 {
+    (void) path;
     r->_errno = ENODEV;                     /* not implemented yet */
     return -1;
 }