diff --git a/tbsetup/libtestbed.pm.in b/tbsetup/libtestbed.pm.in
index e1c9a120b41b0231984b697b578c7a82f8e82b67..7b2e184611bf741f69ac52b14b3130992e5e5055 100644
--- a/tbsetup/libtestbed.pm.in
+++ b/tbsetup/libtestbed.pm.in
@@ -450,6 +450,8 @@ sub TBMakeLogname($)
 sub TBGenSecretKey()
 {
     my $key=`/bin/dd if=/dev/urandom count=128 bs=1 2> /dev/null | /sbin/md5`;
+    return undef
+	if ($?);
     chomp($key);
     return $key;
 }