diff --git a/include/nuttx/mm/iob.h b/include/nuttx/mm/iob.h
index 704d9d7bc20..a530bd996f7 100644
--- a/include/nuttx/mm/iob.h
+++ b/include/nuttx/mm/iob.h
@@ -88,6 +88,8 @@
 #  define IOB_QEMPTY(q)  ((q)->qh_head == NULL)
 #endif
 
+#define IOB_BUFSIZE(p)   CONFIG_IOB_BUFSIZE
+
 /****************************************************************************
  * Public Types
  ****************************************************************************/
diff --git a/mm/iob/iob_clone.c b/mm/iob/iob_clone.c
index 109e3d6bd80..82e319e5439 100644
--- a/mm/iob/iob_clone.c
+++ b/mm/iob/iob_clone.c
@@ -139,7 +139,7 @@ int iob_clone_partial(FAR struct iob_s *iob1, unsigned int len,
 
   while (iob2 != NULL)
     {
-      avail2 = CONFIG_IOB_BUFSIZE - iob2->io_offset;
+      avail2 = IOB_BUFSIZE(iob2) - iob2->io_offset;
       if ((int)(offset2 - avail2) < 0)
         {
           break;
@@ -173,7 +173,7 @@ int iob_clone_partial(FAR struct iob_s *iob1, unsigned int len,
        */
 
       dest   = &iob2->io_data[iob2->io_offset + offset2];
-      avail2 = CONFIG_IOB_BUFSIZE - iob2->io_offset - offset2;
+      avail2 = IOB_BUFSIZE(iob2) - iob2->io_offset - offset2;
 
       /* Copy the smaller of the two and update the srce and destination
        * offsets.
@@ -218,7 +218,7 @@ int iob_clone_partial(FAR struct iob_s *iob1, unsigned int len,
        * transferred?
        */
 
-      if ((int)(offset2 + iob2->io_offset - CONFIG_IOB_BUFSIZE) >= 0 &&
+      if ((int)(offset2 + iob2->io_offset - IOB_BUFSIZE(iob2)) >= 0 &&
           iob1 != NULL)
         {
           ret = iob_next(iob2, throttled, block);
diff --git a/mm/iob/iob_contig.c b/mm/iob/iob_contig.c
index 3d678189f42..7a529ea0d82 100644
--- a/mm/iob/iob_contig.c
+++ b/mm/iob/iob_contig.c
@@ -57,7 +57,7 @@ int iob_contig(FAR struct iob_s *iob, unsigned int len)
    * then you will need to increase CONFIG_IOB_BUFSIZE.
    */
 
-  DEBUGASSERT(len <= CONFIG_IOB_BUFSIZE);
+  DEBUGASSERT(len <= IOB_BUFSIZE(iob));
 
   /* Check if there is already sufficient, contiguous space at the beginning
    * of the packet
diff --git a/mm/iob/iob_copyin.c b/mm/iob/iob_copyin.c
index 0d221ee3b93..fb69aa00c65 100644
--- a/mm/iob/iob_copyin.c
+++ b/mm/iob/iob_copyin.c
@@ -128,7 +128,7 @@ static int iob_copyin_internal(FAR struct iob_s *iob, FAR const uint8_t *src,
 
               /* Yes.. We can extend this buffer to the up to the very end. */
 
-              maxlen = CONFIG_IOB_BUFSIZE - iob->io_offset;
+              maxlen = IOB_BUFSIZE(iob) - iob->io_offset;
 
               /* This is the new buffer length that we need.  Of course,
                * clipped to the maximum possible size in this buffer.
diff --git a/mm/iob/iob_pack.c b/mm/iob/iob_pack.c
index 55b590311f3..6fdce16cbe8 100644
--- a/mm/iob/iob_pack.c
+++ b/mm/iob/iob_pack.c
@@ -86,7 +86,7 @@ FAR struct iob_s *iob_pack(FAR struct iob_s *iob)
            */
 
           ncopy  = next->io_len;
-          navail = CONFIG_IOB_BUFSIZE - iob->io_len;
+          navail = IOB_BUFSIZE(iob) - iob->io_len;
           if (ncopy > navail)
             {
               ncopy = navail;
diff --git a/mm/iob/iob_reserve.c b/mm/iob/iob_reserve.c
index e1964d5d14f..d707f1fa398 100644
--- a/mm/iob/iob_reserve.c
+++ b/mm/iob/iob_reserve.c
@@ -49,9 +49,9 @@ void iob_reserve(FAR struct iob_s *iob, unsigned int reserved)
 
   while (iob != NULL && reserved > 0)
     {
-      if (reserved > CONFIG_IOB_BUFSIZE)
+      if (reserved > IOB_BUFSIZE(iob))
         {
-          offset = CONFIG_IOB_BUFSIZE;
+          offset = IOB_BUFSIZE(iob);
         }
       else
         {
diff --git a/mm/iob/iob_tailroom.c b/mm/iob/iob_tailroom.c
index d0c999156c8..883f220693f 100644
--- a/mm/iob/iob_tailroom.c
+++ b/mm/iob/iob_tailroom.c
@@ -48,5 +48,5 @@ unsigned int iob_tailroom(FAR struct iob_s *iob)
       iob = iob->io_flink;
     }
 
-  return CONFIG_IOB_BUFSIZE - (iob->io_offset + iob->io_len);
+  return IOB_BUFSIZE(iob) - (iob->io_offset + iob->io_len);
 }
diff --git a/mm/iob/iob_update_pktlen.c b/mm/iob/iob_update_pktlen.c
index e6e1fd46e32..a5ad1501356 100644
--- a/mm/iob/iob_update_pktlen.c
+++ b/mm/iob/iob_update_pktlen.c
@@ -74,8 +74,7 @@ int iob_update_pktlen(FAR struct iob_s *iob, unsigned int pktlen,
 
   /* Trim inqueue entries if needed */
 
-  nrequire = (pktlen + offset + CONFIG_IOB_BUFSIZE - 1) /
-             CONFIG_IOB_BUFSIZE;
+  nrequire = (pktlen + offset + IOB_BUFSIZE(iob) - 1) / IOB_BUFSIZE(iob);
   if (nrequire == 0)
     {
       nrequire = 1;
@@ -130,9 +129,9 @@ int iob_update_pktlen(FAR struct iob_s *iob, unsigned int pktlen,
   next = iob;
   while (next != NULL && pktlen > 0)
     {
-      if (pktlen + next->io_offset > CONFIG_IOB_BUFSIZE)
+      if (pktlen + next->io_offset > IOB_BUFSIZE(next))
         {
-          len = CONFIG_IOB_BUFSIZE - next->io_offset;
+          len = IOB_BUFSIZE(next) - next->io_offset;
         }
       else
         {