diff --git a/ssh.c b/ssh.c
index 524a7504..7c4caa57 100644
--- a/ssh.c
+++ b/ssh.c
@@ -849,6 +849,7 @@ static Bignum ssh2_pkt_getmp(void) {
         else
             b[j/2+1] |= ((unsigned char)p[i]);
     }
+    while (b[0] > 1 && b[b[0]] == 0) b[0]--;
     return b;
 }