diff --git a/RNode_Firmware.ino b/RNode_Firmware.ino
index 1f1801a..dfbb9cb 100644
--- a/RNode_Firmware.ino
+++ b/RNode_Firmware.ino
@@ -6,17 +6,17 @@ FIFOBuffer serialFIFO;
 uint8_t serialBuffer[CONFIG_UART_BUFFER_SIZE+1];
 
 FIFOBuffer16 packet_starts;
-size_t packet_starts_buf[CONFIG_QUEUE_MAX_LENGTH+1];
+uint16_t packet_starts_buf[CONFIG_QUEUE_MAX_LENGTH+1];
 
 FIFOBuffer16 packet_lengths;
-size_t packet_lengths_buf[CONFIG_QUEUE_MAX_LENGTH+1];
+uint16_t packet_lengths_buf[CONFIG_QUEUE_MAX_LENGTH+1];
 
 uint8_t packet_queue[CONFIG_QUEUE_SIZE];
 
 volatile uint8_t queue_height = 0;
-volatile size_t queued_bytes = 0;
-volatile size_t queue_cursor = 0;
-volatile size_t current_packet_start = 0;
+volatile uint16_t queued_bytes = 0;
+volatile uint16_t queue_cursor = 0;
+volatile uint16_t current_packet_start = 0;
 volatile bool serial_buffering = false;
 
 char sbuf[128];
@@ -250,7 +250,7 @@ void flushQueue(void) {
   if (!queue_flushing) {
     queue_flushing = true;
 
-    size_t processed = 0;
+    uint16_t processed = 0;
 
     #if MCU_VARIANT == MCU_ESP32
     while (!fifo16_isempty(&packet_starts)) {
@@ -258,12 +258,12 @@ void flushQueue(void) {
     while (!fifo16_isempty_locked(&packet_starts)) {
     #endif
 
-      size_t start = fifo16_pop(&packet_starts);
-      size_t length = fifo16_pop(&packet_lengths);
+      uint16_t start = fifo16_pop(&packet_starts);
+      uint16_t length = fifo16_pop(&packet_lengths);
 
       if (length >= MIN_L && length <= MTU) {
-        for (size_t i = 0; i < length; i++) {
-          size_t pos = (start+i)%CONFIG_QUEUE_SIZE;
+        for (uint16_t i = 0; i < length; i++) {
+          uint16_t pos = (start+i)%CONFIG_QUEUE_SIZE;
           tbuf[i] = packet_queue[pos];
         }
 
@@ -278,11 +278,11 @@ void flushQueue(void) {
   queue_flushing = false;
 }
 
-void transmit(size_t size) {
+void transmit(uint16_t size) {
   if (radio_online) {
     if (!promisc) {
       led_tx_on();
-      size_t  written = 0;
+      uint16_t  written = 0;
       uint8_t header  = random(256) & 0xF0;
 
       if (size > SINGLE_MTU - HEADER_L) {
@@ -292,7 +292,7 @@ void transmit(size_t size) {
       LoRa.beginPacket();
       LoRa.write(header); written++;
 
-      for (size_t i; i < size; i++) {
+      for (uint16_t i; i < size; i++) {
         LoRa.write(tbuf[i]);  
 
         written++;
@@ -314,7 +314,7 @@ void transmit(size_t size) {
       // plain raw LoRa packets with a maximum
       // payload of 255 bytes
       led_tx_on();
-      size_t  written = 0;
+      uint16_t  written = 0;
       
       // Cap packets at 255 bytes
       if (size > SINGLE_MTU) {
@@ -329,7 +329,7 @@ void transmit(size_t size) {
         LoRa.beginPacket(size);
       }
 
-      for (size_t i; i < size; i++) {
+      for (uint16_t i; i < size; i++) {
         LoRa.write(tbuf[i]);
 
         written++;
@@ -350,9 +350,9 @@ void serialCallback(uint8_t sbyte) {
     IN_FRAME = false;
 
     if (!fifo16_isfull(&packet_starts) && queued_bytes < CONFIG_QUEUE_SIZE) {
-        size_t s = current_packet_start;
-        size_t e = queue_cursor-1; if (e == -1) e = CONFIG_QUEUE_SIZE-1;
-        size_t l;
+        uint16_t s = current_packet_start;
+        uint16_t e = queue_cursor-1; if (e == -1) e = CONFIG_QUEUE_SIZE-1;
+        uint16_t l;
 
         if (s != e) {
             l = (s < e) ? e - s + 1 : CONFIG_QUEUE_SIZE - s + e + 1;
diff --git a/Utilities.h b/Utilities.h
index 31c2678..5d7ce58 100644
--- a/Utilities.h
+++ b/Utilities.h
@@ -713,10 +713,10 @@ inline size_t fifo_len(FIFOBuffer *f) {
 
 typedef struct FIFOBuffer16
 {
-  size_t *begin;
-  size_t *end;
-  size_t * volatile head;
-  size_t * volatile tail;
+  uint16_t *begin;
+  uint16_t *end;
+  uint16_t * volatile head;
+  uint16_t * volatile tail;
 } FIFOBuffer16;
 
 inline bool fifo16_isempty(const FIFOBuffer16 *f) {
@@ -727,7 +727,7 @@ inline bool fifo16_isfull(const FIFOBuffer16 *f) {
   return ((f->head == f->begin) && (f->tail == f->end)) || (f->tail == f->head - 1);
 }
 
-inline void fifo16_push(FIFOBuffer16 *f, size_t c) {
+inline void fifo16_push(FIFOBuffer16 *f, uint16_t c) {
   *(f->tail) = c;
 
   if (f->tail == f->end) {
@@ -737,7 +737,7 @@ inline void fifo16_push(FIFOBuffer16 *f, size_t c) {
   }
 }
 
-inline size_t fifo16_pop(FIFOBuffer16 *f) {
+inline uint16_t fifo16_pop(FIFOBuffer16 *f) {
   if(f->head == f->end) {
     f->head = f->begin;
     return *(f->end);
@@ -771,7 +771,7 @@ static inline bool fifo16_isfull_locked(const FIFOBuffer16 *f) {
 }
 
 
-static inline void fifo16_push_locked(FIFOBuffer16 *f, size_t c) {
+static inline void fifo16_push_locked(FIFOBuffer16 *f, uint16_t c) {
   ATOMIC_BLOCK(ATOMIC_RESTORESTATE) {
     fifo16_push(f, c);
   }
@@ -786,11 +786,11 @@ static inline size_t fifo16_pop_locked(FIFOBuffer16 *f) {
 }
 */
 
-inline void fifo16_init(FIFOBuffer16 *f, size_t *buffer, size_t size) {
+inline void fifo16_init(FIFOBuffer16 *f, uint16_t *buffer, uint16_t size) {
   f->head = f->tail = f->begin = buffer;
   f->end = buffer + size;
 }
 
-inline size_t fifo16_len(FIFOBuffer16 *f) {
+inline uint16_t fifo16_len(FIFOBuffer16 *f) {
   return (f->end - f->begin);
 }