diff --git a/core/contiki-default-conf.h b/core/contiki-default-conf.h
index 1628f8a72..93fb2a839 100644
--- a/core/contiki-default-conf.h
+++ b/core/contiki-default-conf.h
@@ -220,13 +220,12 @@
 #define SICSLOWPAN_CONF_FRAG 1
 #endif /* SICSLOWPAN_CONF_FRAG */
 
-/* SICSLOWPAN_CONF_MAC_MAX_PAYLOAD specifies the maximum size of
-   packets before they get fragmented. The default is 127 bytes (the
-   maximum size of a 802.15.4 frame) - 25 bytes (for the 802.15.4 MAC
-   layer header). This can be increased for systems with larger packet
-   sizes. */
+/* SICSLOWPAN_CONF_MAC_MAX_PAYLOAD is the maximum available size for
+   frame headers, link layer security-related overhead,  as well as
+   6LoWPAN payload. By default, SICSLOWPAN_CONF_MAC_MAX_PAYLOAD is
+   127 bytes (MTU of 802.15.4) - 2 bytes (Footer of 802.15.4). */
 #ifndef SICSLOWPAN_CONF_MAC_MAX_PAYLOAD
-#define SICSLOWPAN_CONF_MAC_MAX_PAYLOAD (127 - 25)
+#define SICSLOWPAN_CONF_MAC_MAX_PAYLOAD (127 - 2)
 #endif /* SICSLOWPAN_CONF_MAC_MAX_PAYLOAD */
 
 /* SICSLOWPAN_CONF_COMPRESSION_THRESHOLD sets a lower threshold for
diff --git a/core/net/ipv6/sicslowpan.c b/core/net/ipv6/sicslowpan.c
index 9a854ae4b..133d66e4b 100644
--- a/core/net/ipv6/sicslowpan.c
+++ b/core/net/ipv6/sicslowpan.c
@@ -155,11 +155,13 @@ void uip_log(char *msg);
 /** @} */
 
 
-/** \brief Size of the 802.15.4 payload (127byte - 25 for MAC header) */
+/** \brief Maximum available size for frame headers,
+           link layer security-related overhead, as well as
+           6LoWPAN payload. */
 #ifdef SICSLOWPAN_CONF_MAC_MAX_PAYLOAD
 #define MAC_MAX_PAYLOAD SICSLOWPAN_CONF_MAC_MAX_PAYLOAD
 #else /* SICSLOWPAN_CONF_MAC_MAX_PAYLOAD */
-#define MAC_MAX_PAYLOAD 102
+#define MAC_MAX_PAYLOAD (127 - 2)
 #endif /* SICSLOWPAN_CONF_MAC_MAX_PAYLOAD */
 
 
@@ -1361,6 +1363,7 @@ static uint8_t
 output(const uip_lladdr_t *localdest)
 {
   int framer_hdrlen;
+  int max_payload;
 
   /* The MAC address of the destination of the packet */
   linkaddr_t dest;
@@ -1443,8 +1446,9 @@ output(const uip_lladdr_t *localdest)
 #else /* USE_FRAMER_HDRLEN */
   framer_hdrlen = 21;
 #endif /* USE_FRAMER_HDRLEN */
+  max_payload = MAC_MAX_PAYLOAD - framer_hdrlen - NETSTACK_LLSEC.get_overhead();
 
-  if((int)uip_len - (int)uncomp_hdr_len > (int)MAC_MAX_PAYLOAD - framer_hdrlen - (int)packetbuf_hdr_len) {
+  if((int)uip_len - (int)uncomp_hdr_len > max_payload - (int)packetbuf_hdr_len) {
 #if SICSLOWPAN_CONF_FRAG
     struct queuebuf *q;
     /*
@@ -1477,7 +1481,7 @@ output(const uip_lladdr_t *localdest)
 
     /* Copy payload and send */
     packetbuf_hdr_len += SICSLOWPAN_FRAG1_HDR_LEN;
-    packetbuf_payload_len = (MAC_MAX_PAYLOAD - framer_hdrlen - packetbuf_hdr_len) & 0xfffffff8;
+    packetbuf_payload_len = (max_payload - packetbuf_hdr_len) & 0xfffffff8;
     PRINTFO("(len %d, tag %d)\n", packetbuf_payload_len, my_tag);
     memcpy(packetbuf_ptr + packetbuf_hdr_len,
            (uint8_t *)UIP_IP_BUF + uncomp_hdr_len, packetbuf_payload_len);
@@ -1513,7 +1517,7 @@ output(const uip_lladdr_t *localdest)
 /*       uip_htons((SICSLOWPAN_DISPATCH_FRAGN << 8) | uip_len); */
     SET16(PACKETBUF_FRAG_PTR, PACKETBUF_FRAG_DISPATCH_SIZE,
           ((SICSLOWPAN_DISPATCH_FRAGN << 8) | uip_len));
-    packetbuf_payload_len = (MAC_MAX_PAYLOAD - framer_hdrlen - packetbuf_hdr_len) & 0xfffffff8;
+    packetbuf_payload_len = (max_payload - packetbuf_hdr_len) & 0xfffffff8;
     while(processed_ip_out_len < uip_len) {
       PRINTFO("sicslowpan output: fragment ");
       PACKETBUF_FRAG_PTR[PACKETBUF_FRAG_OFFSET] = processed_ip_out_len >> 3;
diff --git a/core/net/llsec/llsec.h b/core/net/llsec/llsec.h
index 0889459b3..965a1b06d 100644
--- a/core/net/llsec/llsec.h
+++ b/core/net/llsec/llsec.h
@@ -85,6 +85,9 @@ struct llsec_driver {
    * filters out injected or replayed frames.
    */
   void (* input)(void);
+  
+  /** Returns the security-related overhead per frame in bytes */
+  uint8_t (* get_overhead)(void);
 };
 
 #endif /* LLSEC_H_ */
diff --git a/core/net/llsec/noncoresec/noncoresec.c b/core/net/llsec/noncoresec/noncoresec.c
index 1e6a2e7aa..1d0015645 100644
--- a/core/net/llsec/noncoresec/noncoresec.c
+++ b/core/net/llsec/noncoresec/noncoresec.c
@@ -65,6 +65,8 @@
                          0x0C , 0x0D , 0x0E , 0x0F }
 #endif /* NONCORESEC_CONF_KEY */
 
+#define SECURITY_HEADER_LENGTH 5
+
 #define DEBUG 0
 #if DEBUG
 #include <stdio.h>
@@ -192,6 +194,12 @@ input(void)
   NETSTACK_NETWORK.input();
 }
 /*---------------------------------------------------------------------------*/
+static uint8_t
+get_overhead(void)
+{
+  return SECURITY_HEADER_LENGTH + LLSEC802154_MIC_LENGTH;
+}
+/*---------------------------------------------------------------------------*/
 static void
 bootstrap(llsec_on_bootstrapped_t on_bootstrapped)
 {
@@ -205,7 +213,8 @@ const struct llsec_driver noncoresec_driver = {
   bootstrap,
   send,
   on_frame_created,
-  input
+  input,
+  get_overhead
 };
 /*---------------------------------------------------------------------------*/
 
diff --git a/core/net/llsec/nullsec.c b/core/net/llsec/nullsec.c
index 4fc146ce5..040e9ed76 100644
--- a/core/net/llsec/nullsec.c
+++ b/core/net/llsec/nullsec.c
@@ -73,12 +73,19 @@ input(void)
   NETSTACK_NETWORK.input();
 }
 /*---------------------------------------------------------------------------*/
+static uint8_t
+get_overhead(void)
+{
+  return 0;
+}
+/*---------------------------------------------------------------------------*/
 const struct llsec_driver nullsec_driver = {
   "nullsec",
   bootstrap,
   send,
   on_frame_created,
-  input
+  input,
+  get_overhead
 };
 /*---------------------------------------------------------------------------*/