diff --git a/run/check.sh b/run/check.sh
index 8cfc61b..5ffab1f 100644
--- a/run/check.sh
+++ b/run/check.sh
@@ -21,6 +21,11 @@ rest=${rest#*:}
 rest=${rest%%,*}
 PORT=${rest%%\"*}
 
+if [ -z "${PORT}" ]; then
+  echo "Guest has not set a portnumber yet.."
+  exit 1
+fi
+
 # Retrieve the IP address
 
 if [[ ! "${RESPONSE}" =~ "eth0" ]] ; then
@@ -34,6 +39,11 @@ rest=${rest#*:}
 rest=${rest#*\"}
 IP=${rest%%\"*}
 
+if [ -z "${IP}" ]; then
+  echo "Guest has not received an IP yet.."
+  exit 1
+fi
+
 if ! curl -m 3 -ILfSs "http://${IP}:${PORT}/" > /dev/null; then
   echo "Failed to reach ${IP}:${PORT}"
   exit 1