diff --git a/cluster/gce/util.sh b/cluster/gce/util.sh
index 598c569b621..565e105ece8 100755
--- a/cluster/gce/util.sh
+++ b/cluster/gce/util.sh
@@ -1594,7 +1594,8 @@ function create-certs {
   local -r primary_cn="${1}"
 
   # Determine extra certificate names for master
-  local octets=($(echo "${SERVICE_CLUSTER_IP_RANGE}" | sed -e 's|/.*||' -e 's/\./ /g'))
+  local octets
+  read -r -a octets <<< "$(echo "${SERVICE_CLUSTER_IP_RANGE}" | sed -e 's|/.*||' -e 's/\./ /g')"
   ((octets[3]+=1))
   local -r service_ip=$(echo "${octets[*]}" | sed 's/ /./g')
   local sans=""