diff --git a/slapos/recipe/check_url_available/template/check_url.in b/slapos/recipe/check_url_available/template/check_url.in
index b4f5c0ef3980b9657b8948b23af55b0d1ad831d7..61d3b3b4765ebd5dd346bca0963b75c2f2fbe668 100644
--- a/slapos/recipe/check_url_available/template/check_url.in
+++ b/slapos/recipe/check_url_available/template/check_url.in
@@ -13,8 +13,8 @@ fi
 
 if [ -s "$F_TIMEOUT" ]; then
   TIMEOUT=$(cat $F_TIMEOUT)
-  re="^[0-9]+$"
-  if ! [[ $TIMEOUT =~ $re ]]; then
+  result=$(echo $TIMEOUT | grep -E ^[0-9]+$)
+  if [ -z $result ]; then
     # Not an integer
     TIMEOUT=20
   fi