diff --git a/deploy/docker.sh b/deploy/docker.sh
index 451d5d00..3aa1b2cd 100755
--- a/deploy/docker.sh
+++ b/deploy/docker.sh
@@ -275,6 +275,7 @@ _check_curl_version() {
 
   if [ "$_major$_minor" -lt "740" ]; then
     _err "curl v$_cversion doesn't support unit socket"
+    _err "Please upgrade to curl 7.40 or later."
     return 1
   fi
   if [ "$_major$_minor" -lt "750" ]; then