diff --git a/marshal.c b/marshal.c
index a8371b66..f0612a85 100644
--- a/marshal.c
+++ b/marshal.c
@@ -11,7 +11,7 @@ void BinarySink_put_data(BinarySink *bs, const void *data, size_t len)
     bs->write(bs, data, len);
 }
 
-void BinarySink_put_padding(BinarySink *bs, unsigned char padbyte, size_t len)
+void BinarySink_put_padding(BinarySink *bs, size_t len, unsigned char padbyte)
 {
     char buf[16];
     memset(buf, padbyte, sizeof(buf));
diff --git a/marshal.h b/marshal.h
index 0debe82f..2aa0301a 100644
--- a/marshal.h
+++ b/marshal.h
@@ -111,8 +111,8 @@ struct BinarySink {
     BinarySink_put_mp_ssh2(BinarySink_UPCAST(bs), val)
 
 /* Padding with a specified byte. */
-#define put_padding(bs, padbyte, len) \
-    BinarySink_put_padding(BinarySink_UPCAST(bs), padbyte, len)
+#define put_padding(bs, len, padbyte) \
+    BinarySink_put_padding(BinarySink_UPCAST(bs), len, padbyte)
 
 /* Fallback: just emit raw data bytes, using a syntax that matches the
  * rest of these macros. */
@@ -130,7 +130,7 @@ struct BinarySink {
  * declaration(s) of their other parameter type(s) are in scope.
  */
 void BinarySink_put_data(BinarySink *, const void *data, size_t len);
-void BinarySink_put_padding(BinarySink *, unsigned char padbyte, size_t len);
+void BinarySink_put_padding(BinarySink *, size_t len, unsigned char padbyte);
 void BinarySink_put_byte(BinarySink *, unsigned char);
 void BinarySink_put_bool(BinarySink *, int);
 void BinarySink_put_uint16(BinarySink *, unsigned long);
diff --git a/ssh2bpp.c b/ssh2bpp.c
index da0ac900..0ea1f793 100644
--- a/ssh2bpp.c
+++ b/ssh2bpp.c
@@ -582,7 +582,7 @@ static void ssh2_bpp_format_packet(BinaryPacketProtocol *bpp, PktOut *pkt)
                                       s->out.sequence);
     }
 
-    put_padding(pkt, 0, maclen);
+    put_padding(pkt, maclen, 0);
 
     if (s->out.mac && s->out.etm_mode) {
         /*