diff --git a/themes/hugo-sustain/layouts/partials/head.html b/themes/hugo-sustain/layouts/partials/head.html
index bb97323..82b96e4 100644
--- a/themes/hugo-sustain/layouts/partials/head.html
+++ b/themes/hugo-sustain/layouts/partials/head.html
@@ -31,7 +31,7 @@
     <link rel="stylesheet" type="text/css" href="{{ .Site.BaseURL }}css/fontawesome/css/all.min.css" />
     <link rel="stylesheet" type="text/css" href="{{ .Site.BaseURL }}css/fonts.css" />
     {{- range .Site.Params.custom_css }}
-    <link rel="stylesheet" href="{{ $.Site.BaseURL}}{{ . }}?v={{ md5 hugo.BuildDate }}" />
+    <link rel="stylesheet" href="{{ $.Site.BaseURL}}{{ . }}?v={{ md5 time.Now.Unix }}" />
     {{- end }}
 
     {{ "<!-- Open Graph meta-data (e.g. Facebook) -->" | safeHTML }}