diff --git a/drivers/net/telnet.c b/drivers/net/telnet.c
index fb7cea5b57..241ef778f6 100644
--- a/drivers/net/telnet.c
+++ b/drivers/net/telnet.c
@@ -359,7 +359,7 @@ static ssize_t telnet_receive(FAR struct telnet_dev_s *priv,
   int nread;
   uint8_t ch;
 
-  ninfo("srclen: %d destlen: %d\n", srclen, destlen);
+  ninfo("srclen: %zd destlen: %zd\n", srclen, destlen);
 
   for (nread = 0; srclen > 0 && nread < destlen; srclen--)
     {
@@ -809,7 +809,7 @@ static ssize_t telnet_read(FAR struct file *filep, FAR char *buffer,
   ssize_t nread = 0;
   int ret;
 
-  ninfo("len: %d\n", len);
+  ninfo("len: %zd\n", len);
 
   /* First, handle the case where there are still valid bytes left in the
    * I/O buffer from the last time that read was called.  NOTE:  Much of
@@ -892,7 +892,7 @@ static ssize_t telnet_write(FAR struct file *filep, FAR const char *buffer,
   char ch;
   bool eol;
 
-  ninfo("len: %d\n", len);
+  ninfo("len: %zd\n", len);
 
   /* Process each character from the user buffer */
 
@@ -917,7 +917,7 @@ static ssize_t telnet_write(FAR struct file *filep, FAR const char *buffer,
           ret = psock_send(&priv->td_psock, priv->td_txbuffer, ncopied, 0);
           if (ret < 0)
             {
-              nerr("ERROR: psock_send failed '%s': %d\n",
+              nerr("ERROR: psock_send failed '%s': %zd\n",
                    priv->td_txbuffer, ret);
               return ret;
             }
@@ -935,7 +935,7 @@ static ssize_t telnet_write(FAR struct file *filep, FAR const char *buffer,
       ret = psock_send(&priv->td_psock, priv->td_txbuffer, ncopied, 0);
       if (ret < 0)
         {
-          nerr("ERROR: psock_send failed '%s': %d\n",
+          nerr("ERROR: psock_send failed '%s': %zd\n",
                priv->td_txbuffer, ret);
           return ret;
         }