diff --git a/prometheus/files/exporter.systemd.jinja b/prometheus/files/exporter.systemd.jinja
index 9d3a893..a1d7c2f 100644
--- a/prometheus/files/exporter.systemd.jinja
+++ b/prometheus/files/exporter.systemd.jinja
@@ -1,6 +1,6 @@
 [Unit]
 Description=Prometheus {{ svc }} Exporter
-{%- if url is string %}
+{%- if url is string and url is not None %}
 Documentation={{ url }}
 {%- endif %}
 Wants=basic.target