diff --git a/mksnap.sh b/mksnap.sh
index 8aed89a6346203258204929af330abcc70fb29c5..843427b22ad373e6b7f6b27f9a9c99f7ecaf043c 100755
--- a/mksnap.sh
+++ b/mksnap.sh
@@ -11,8 +11,8 @@ SNAPSHOTDIR=/hosts/www/www/htdocs/IAM/homepages/claus/download/alberta/snapshots
 NSNAPSHOTS=10 # keep only the most recent 10 snapshots
 
 # Pray that we have a running ssh-agent (and only one ...)
-SSH_AGENT_PID=`ps -u claus  |grep ssh-agent|awk '{ print $1; }'`
-SSH_AUTH_SOCK=`find /tmp -user claus -name "agent.[0-9]*"`
+: ${SSH_AGENT_PID=`ps -u claus  |grep ssh-agent|awk '{ print $1; }'`}
+: ${SSH_AUTH_SOCK=`find /tmp -user claus -name "agent.[0-9]*"`}
 export SSH_AGENT_PID SSH_AUTH_SOCK
 
 if test -z "${SSH_AGENT_PID}" -o -z "${SSH_AUTH_SOCK}"; then