--- src/triggers/post-compile/ssh-authkeys-split.orig	2017-07-02 14:01:25 UTC
+++ src/triggers/post-compile/ssh-authkeys-split
@@ -66,7 +66,7 @@ do
             echo 1>&2 "ssh-authkeys-split: bad line $seq in keydir/$k"
             rm -f $f
         fi
-        (( seq++ ))
+        seq=$(( $seq + 1 ))
     done < $k
 
     # now delete the original file