diff --git a/core/dev/cc2420.c b/core/dev/cc2420.c
index 7a5d35a93..8e8a1b657 100644
--- a/core/dev/cc2420.c
+++ b/core/dev/cc2420.c
@@ -139,7 +139,7 @@ static int cc2420_send(const void *data, unsigned short len);
 static int cc2420_receiving_packet(void);
 static int pending_packet(void);
 static int cc2420_cca(void);
-static int detected_energy(void);
+/*static int detected_energy(void);*/
 
 signed char cc2420_last_rssi;
 uint8_t cc2420_last_correlation;
diff --git a/core/net/mac/cxmac.c b/core/net/mac/cxmac.c
index d01750156..84e945ead 100644
--- a/core/net/mac/cxmac.c
+++ b/core/net/mac/cxmac.c
@@ -454,7 +454,7 @@ send_packet(void)
     packetbuf_attr(PACKETBUF_ATTR_ERELIABLE);
   len = NETSTACK_FRAMER.create();
   strobe_len = len + sizeof(struct cxmac_hdr);
-  if(len == 0 || strobe_len > sizeof(strobe)) {
+  if(len == 0 || strobe_len > (int)sizeof(strobe)) {
     /* Failed to send */
    PRINTF("cxmac: send failed, too large header\n");
     return MAC_TX_ERR_FATAL;
diff --git a/core/net/mac/framer-802154.c b/core/net/mac/framer-802154.c
index 02ea4bfe1..ba566de78 100644
--- a/core/net/mac/framer-802154.c
+++ b/core/net/mac/framer-802154.c
@@ -56,8 +56,8 @@
 
 static uint8_t mac_dsn;
 static uint8_t initialized = 0;
-const static uint16_t mac_dst_pan_id = IEEE802154_PANID;
-const static uint16_t mac_src_pan_id = IEEE802154_PANID;
+static const uint16_t mac_dst_pan_id = IEEE802154_PANID;
+static const uint16_t mac_src_pan_id = IEEE802154_PANID;
 
 /*---------------------------------------------------------------------------*/
 static int
diff --git a/core/net/mac/xmac.c b/core/net/mac/xmac.c
index fcdb88924..547e93b8f 100644
--- a/core/net/mac/xmac.c
+++ b/core/net/mac/xmac.c
@@ -455,7 +455,9 @@ send_packet(void)
   rtimer_clock_t t;
   rtimer_clock_t encounter_time = 0;
   int strobes;
+#if 0
   struct xmac_hdr *hdr;
+#endif
   uint8_t got_strobe_ack = 0;
   uint8_t got_ack = 0;
   uint8_t strobe[MAX_STROBE_SIZE];
@@ -495,7 +497,7 @@ send_packet(void)
   packetbuf_set_attr(PACKETBUF_ATTR_MAC_ACK, 1);
   len = NETSTACK_FRAMER.create();
   strobe_len = len + sizeof(struct xmac_hdr);
-  if(len == 0 || strobe_len > sizeof(strobe)) {
+  if(len == 0 || strobe_len > (int)sizeof(strobe)) {
     /* Failed to send */
    PRINTF("xmac: send failed, too large header\n");
     return MAC_TX_ERR_FATAL;
@@ -602,9 +604,9 @@ send_packet(void)
 
       while(got_strobe_ack == 0 &&
 	    RTIMER_CLOCK_LT(RTIMER_NOW(), t + xmac_config.strobe_wait_time)) {
+#if 0
 	rtimer_clock_t now = RTIMER_NOW();
 
-#if 0
 	/* See if we got an ACK */
 	packetbuf_clear();
 	len = NETSTACK_RADIO.read(packetbuf_dataptr(), PACKETBUF_SIZE);
@@ -647,7 +649,9 @@ send_packet(void)
 #endif
           off();
 	} else {
+#if 0
 	  rtimer_clock_t wt;
+#endif
           on();
 	  NETSTACK_RADIO.send(strobe, strobe_len);
 #if 0
diff --git a/core/net/rime/collect-link-estimate.c b/core/net/rime/collect-link-estimate.c
index ff93cdbbb..50b0ac40e 100644
--- a/core/net/rime/collect-link-estimate.c
+++ b/core/net/rime/collect-link-estimate.c
@@ -108,9 +108,6 @@ collect_link_estimate_update_rx(struct collect_link_estimate *n)
 uint16_t
 collect_link_estimate(struct collect_link_estimate *le)
 {
-  int i;
-  uint16_t etx;
-
   if(le->num_estimates == 0) {
     return INITIAL_LINK_ESTIMATE * COLLECT_LINK_ESTIMATE_UNIT;
   }
diff --git a/core/net/rpl/rpl-dag.c b/core/net/rpl/rpl-dag.c
index 330d79b21..10c57039d 100644
--- a/core/net/rpl/rpl-dag.c
+++ b/core/net/rpl/rpl-dag.c
@@ -419,7 +419,7 @@ rpl_get_dag(int instance_id)
 rpl_of_t *
 rpl_find_of(rpl_ocp_t ocp)
 {
-  int i;
+  unsigned int i;
 
   for(i = 0;
       i < sizeof(objective_functions) / sizeof(objective_functions[0]); 
diff --git a/core/net/uip-debug.c b/core/net/uip-debug.c
index 2695169f5..60ec30f86 100644
--- a/core/net/uip-debug.c
+++ b/core/net/uip-debug.c
@@ -46,7 +46,8 @@ uip_debug_ipaddr_print(const uip_ipaddr_t *addr)
 {
 #if UIP_CONF_IPV6
   uint16_t a;
-  int i, f;
+  unsigned int i;
+  int f;
   for(i = 0, f = 0; i < sizeof(uip_ipaddr_t); i += 2) {
     a = (addr->u8[i] << 8) + addr->u8[i + 1];
     if(a == 0 && f >= 0) {
@@ -70,7 +71,7 @@ uip_debug_ipaddr_print(const uip_ipaddr_t *addr)
 void
 uip_debug_lladdr_print(const uip_lladdr_t *addr)
 {
-  int i;
+  unsigned int i;
   for(i = 0; i < sizeof(uip_lladdr_t); i++) {
     if(i > 0) {
       printf(":");
diff --git a/core/net/uiplib.c b/core/net/uiplib.c
index 3add7dd2c..630385373 100644
--- a/core/net/uiplib.c
+++ b/core/net/uiplib.c
@@ -47,7 +47,8 @@ uiplib_ipaddrconv(const char *addrstr, uip_ipaddr_t *ipaddr)
 {
 #if UIP_CONF_IPV6
   uint16_t value;
-  int tmp, len, zero;
+  int tmp, zero;
+  unsigned int len;
   char c = 0;  //gcc warning if not initialized
 
   value = 0;
diff --git a/core/sys/timetable-aggregate.c b/core/sys/timetable-aggregate.c
index 5c35b035d..391f472dd 100644
--- a/core/sys/timetable-aggregate.c
+++ b/core/sys/timetable-aggregate.c
@@ -147,7 +147,7 @@ void
 timetable_aggregate_compute_detailed(struct timetable_aggregate *a,
 				     struct timetable *timetable)
 {
-  int i;
+  unsigned int i;
   rtimer_clock_t t;
   
   t = timetable->timestamps[0].time;
@@ -179,7 +179,8 @@ void
 timetable_aggregate_compute_categories(struct timetable_aggregate *a,
 				       struct timetable *timetable)
 {
-  int i,j;
+  unsigned int i;
+  int j;
   rtimer_clock_t t;
   uint16_t categories[XXX_HACK_MAX_CATEGORIES];
   int categories_ptr = 0;
diff --git a/core/sys/timetable.c b/core/sys/timetable.c
index 5fc1481b1..fe30ac166 100644
--- a/core/sys/timetable.c
+++ b/core/sys/timetable.c
@@ -118,7 +118,7 @@ timetable_init(void)
 void
 timetable_print(struct timetable *t)
 {
-  int i;
+  unsigned int i;
   int time;
   
   time = t->timestamps[0].time;
diff --git a/platform/sky/dev/xmem.c b/platform/sky/dev/xmem.c
index f7f3dee3a..46315d3fa 100644
--- a/platform/sky/dev/xmem.c
+++ b/platform/sky/dev/xmem.c
@@ -200,7 +200,7 @@ xmem_pread(void *_p, int size, unsigned long offset)
   return size;
 }
 /*---------------------------------------------------------------------------*/
-static const char *
+static const unsigned char *
 program_page(unsigned long offset, const unsigned char *p, int nbytes)
 {
   const unsigned char *end = p + nbytes;