diff --git a/ansible/roles/forrest/files/prometheus/blackbox.yml b/ansible/roles/forrest/files/prometheus/blackbox.yml
index 6e40e5a..df0ac9b 100644
--- a/ansible/roles/forrest/files/prometheus/blackbox.yml
+++ b/ansible/roles/forrest/files/prometheus/blackbox.yml
@@ -2,6 +2,8 @@ modules:
   http:
     prober: http
     timeout: 10s
+    http:
+      preferred_ip_protocol: ip4  # Docker network is v4 only
 
   https_redir:
     prober: http
@@ -14,3 +16,4 @@ modules:
       fail_if_header_not_matches:
         - header: Location
           regexp: ^https
+      preferred_ip_protocol: ip4  # Docker network is v4 only