diff --git a/roles/service-grafana/tasks/main.yml b/roles/service-grafana/tasks/main.yml
index 622d503..00306b4 100644
--- a/roles/service-grafana/tasks/main.yml
+++ b/roles/service-grafana/tasks/main.yml
@@ -60,7 +60,7 @@
     database: "yanic"
 
 - name: add prometheus datasource
-  when: prometheus_present is defined
+  when: '"prometheus" in prometheus_components'
   grafana_datasource:
     name: "prometheus"
     grafana_url: "http://localhost:3000"
diff --git a/roles/service-prometheus/tasks/prometheus.yml b/roles/service-prometheus/tasks/prometheus.yml
index 5236877..c66e57d 100644
--- a/roles/service-prometheus/tasks/prometheus.yml
+++ b/roles/service-prometheus/tasks/prometheus.yml
@@ -5,7 +5,6 @@
 
 - name: set internal variables for convenience
   set_fact:
-    prometheus_present: yes
     prometheus_daemon_dir: "{{ prometheus_install_path }}/prometheus-{{ prometheus_version }}.linux-amd64"
     prometheus_tarball_url: "https://github.com/prometheus/prometheus/releases/download/v{{ prometheus_version }}/prometheus-{{ prometheus_version }}.linux-amd64.tar.gz"