diff --git a/src/channels.c b/src/channels.c
index ad1ed81d..15e1e668 100644
--- a/src/channels.c
+++ b/src/channels.c
@@ -478,7 +478,7 @@ SSH_PACKET_CALLBACK(channel_rcv_data){
   len = ssh_string_len(str);
 
   ssh_log(session, SSH_LOG_PROTOCOL,
-      "Channel receiving %zu bytes data in %d (local win=%d remote win=%d)",
+      "Channel receiving %" PRIdS " bytes data in %d (local win=%d remote win=%d)",
       len,
       is_stderr,
       channel->local_window,
@@ -487,7 +487,7 @@ SSH_PACKET_CALLBACK(channel_rcv_data){
   /* What shall we do in this case? Let's accept it anyway */
   if (len > channel->local_window) {
     ssh_log(session, SSH_LOG_RARE,
-        "Data packet too big for our window(%zu vs %d)",
+        "Data packet too big for our window(%" PRIdS " vs %d)",
         len,
         channel->local_window);
   }
diff --git a/src/channels1.c b/src/channels1.c
index d18aa96c..e607b132 100644
--- a/src/channels1.c
+++ b/src/channels1.c
@@ -232,7 +232,7 @@ SSH_PACKET_CALLBACK(ssh_packet_data1){
     }
 
     ssh_log(session, SSH_LOG_PROTOCOL,
-        "Adding %zu bytes data in %d",
+        "Adding %" PRIdS " bytes data in %d",
         ssh_string_len(str), is_stderr);
 
     if (channel_default_bufferize(channel, ssh_string_data(str), ssh_string_len(str),
diff --git a/src/kex.c b/src/kex.c
index c4723a2b..2c7276b2 100644
--- a/src/kex.c
+++ b/src/kex.c
@@ -761,7 +761,7 @@ SSH_PACKET_CALLBACK(ssh_packet_publickey1){
    }
 
    bits = ssh_string_len(enc_session) * 8 - 7;
-   ssh_log(session, SSH_LOG_PROTOCOL, "%d bits, %zu bytes encrypted session",
+   ssh_log(session, SSH_LOG_PROTOCOL, "%d bits, %" PRIdS " bytes encrypted session",
        bits, ssh_string_len(enc_session));
    bits = htons(bits);
    /* the encrypted mpint */
diff --git a/src/sftp.c b/src/sftp.c
index 58859b7f..7cf0042c 100644
--- a/src/sftp.c
+++ b/src/sftp.c
@@ -1817,7 +1817,7 @@ ssize_t sftp_read(sftp_file handle, void *buf, size_t count) {
       if (ssh_string_len(datastring) > count) {
         ssh_set_error(sftp->session, SSH_FATAL,
             "Received a too big DATA packet from sftp server: "
-            "%zu and asked for %zu",
+            "%" PRIdS " and asked for %" PRIdS,
             ssh_string_len(datastring), count);
         ssh_string_free(datastring);
         return -1;
@@ -1938,7 +1938,7 @@ int sftp_async_read(sftp_file file, void *data, uint32_t size, uint32_t id){
       if (ssh_string_len(datastring) > size) {
         ssh_set_error(sftp->session, SSH_FATAL,
             "Received a too big DATA packet from sftp server: "
-            "%zu and asked for %u",
+            "%" PRIdS " and asked for %u",
             ssh_string_len(datastring), size);
         ssh_string_free(datastring);
         sftp_leave_function();