diff --git a/src/rt/circular_buffer.cpp b/src/rt/circular_buffer.cpp
index ee9cc58e9a7..fd389850493 100644
--- a/src/rt/circular_buffer.cpp
+++ b/src/rt/circular_buffer.cpp
@@ -14,8 +14,8 @@ is_power_of_two(size_t value) {
 
 circular_buffer::circular_buffer(rust_dom *dom, size_t unit_sz) :
     dom(dom),
+    unit_sz(unit_sz),
     _buffer_sz(INITIAL_CIRCULAR_BUFFFER_SIZE_IN_UNITS * unit_sz),
-    _unit_sz(unit_sz),
     _next(0),
     _unread(0),
     _buffer((uint8_t *)dom->calloc(_buffer_sz)) {
@@ -47,8 +47,8 @@ circular_buffer::transfer(void *dst) {
     I(dom, dst);
     I(dom, is_power_of_two(_buffer_sz));
     uint8_t *ptr = (uint8_t *) dst;
-    for (size_t i = 0; i < _unread; i += _unit_sz) {
-        memcpy(&ptr[i], &_buffer[(_next + i) & (_buffer_sz - 1)], _unit_sz);
+    for (size_t i = 0; i < _unread; i += unit_sz) {
+        memcpy(&ptr[i], &_buffer[(_next + i) & (_buffer_sz - 1)], unit_sz);
     }
 }
 
@@ -74,16 +74,16 @@ circular_buffer::enqueue(void *src) {
     dom->log(rust_log::MEM | rust_log::COMM,
              "circular_buffer enqueue "
              "unread: %d, buffer_sz: %d, unit_sz: %d",
-             _unread, _buffer_sz, _unit_sz);
+             _unread, _buffer_sz, unit_sz);
 
     I(dom, is_power_of_two(_buffer_sz));
     I(dom, _unread < _buffer_sz);
-    I(dom, _unread + _unit_sz <= _buffer_sz);
+    I(dom, _unread + unit_sz <= _buffer_sz);
 
     // Copy data
     size_t i = (_next + _unread) & (_buffer_sz - 1);
-    memcpy(&_buffer[i], src, _unit_sz);
-    _unread += _unit_sz;
+    memcpy(&_buffer[i], src, unit_sz);
+    _unread += unit_sz;
 
     dom->log(rust_log::MEM | rust_log::COMM,
              "circular_buffer pushed data at index: %d", i);
@@ -95,24 +95,25 @@ circular_buffer::enqueue(void *src) {
  */
 void
 circular_buffer::dequeue(void *dst) {
-    I(dom, dst);
-    I(dom, _unit_sz > 0);
-    I(dom, _unread >= _unit_sz);
+    I(dom, unit_sz > 0);
+    I(dom, _unread >= unit_sz);
     I(dom, _unread <= _buffer_sz);
     I(dom, _buffer);
 
-    memcpy(dst, &_buffer[_next], _unit_sz);
+    if (dst != NULL) {
+        memcpy(dst, &_buffer[_next], unit_sz);
+    }
     dom->log(rust_log::MEM | rust_log::COMM,
              "shifted data from index %d", _next);
-    _unread -= _unit_sz;
-    _next += _unit_sz;
+    _unread -= unit_sz;
+    _next += unit_sz;
     I(dom, _next <= _buffer_sz);
     if (_next == _buffer_sz) {
         _next = 0;
     }
 
     // Shrink if possible.
-    if (_buffer_sz >= INITIAL_CIRCULAR_BUFFFER_SIZE_IN_UNITS * _unit_sz &&
+    if (_buffer_sz >= INITIAL_CIRCULAR_BUFFFER_SIZE_IN_UNITS * unit_sz &&
         _unread <= _buffer_sz / 4) {
         dom->log(rust_log::MEM | rust_log::COMM,
                  "circular_buffer is shrinking to %d bytes", _buffer_sz / 2);
diff --git a/src/rt/circular_buffer.h b/src/rt/circular_buffer.h
index 3d11b37fb78..dc4160d8f33 100644
--- a/src/rt/circular_buffer.h
+++ b/src/rt/circular_buffer.h
@@ -12,6 +12,8 @@ circular_buffer : public dom_owned<circular_buffer> {
 
 public:
     rust_dom *dom;
+    // Size of the data unit in bytes.
+    const size_t unit_sz;
     circular_buffer(rust_dom *dom, size_t unit_sz);
     ~circular_buffer();
     void transfer(void *dst);
@@ -25,9 +27,6 @@ private:
     // (x & (_buffer_sz - 1)).
     size_t _buffer_sz;
 
-    // Size of the data unit in bytes.
-    size_t _unit_sz;
-
     // Byte offset within the buffer where to read the next unit of data.
     size_t _next;