diff --git a/test/test_custom/test_location-per-vhost.yml b/test/test_custom/test_location-per-vhost.yml
index 676712c..07f0817 100644
--- a/test/test_custom/test_location-per-vhost.yml
+++ b/test/test_custom/test_location-per-vhost.yml
@@ -27,4 +27,4 @@ services:
       - "83"
     environment:
       WEB_PORTS: "83"
-      VIRTUAL_HOST: ~^regex.*\.nginx-proxy\.example$$
+      VIRTUAL_HOST: ~^regex.*\.nginx-proxy\.example$$ # we need to double the `$` because of docker compose variable interpolation
diff --git a/test/test_custom/test_per-vhost.yml b/test/test_custom/test_per-vhost.yml
index 3680358..317e208 100644
--- a/test/test_custom/test_per-vhost.yml
+++ b/test/test_custom/test_per-vhost.yml
@@ -27,4 +27,4 @@ services:
       - "83"
     environment:
       WEB_PORTS: "83"
-      VIRTUAL_HOST: ~^regex.*\.nginx-proxy\.example$$
+      VIRTUAL_HOST: ~^regex.*\.nginx-proxy\.example$$ # we need to double the `$` because of docker compose variable interpolation
diff --git a/test/test_htpasswd/test_htpasswd-regex-virtual-host.yml b/test/test_htpasswd/test_htpasswd-regex-virtual-host.yml
index ba9d9ef..9eac0d1 100644
--- a/test/test_htpasswd/test_htpasswd-regex-virtual-host.yml
+++ b/test/test_htpasswd/test_htpasswd-regex-virtual-host.yml
@@ -5,4 +5,4 @@ services:
       - "80"
     environment:
       WEB_PORTS: "80"
-      VIRTUAL_HOST: ~^regex.*\.nginx-proxy\.example$$
+      VIRTUAL_HOST: ~^regex.*\.nginx-proxy\.example$$ # we need to double the `$` because of docker compose variable interpolation