diff --git a/instances/heimdall/configuration.nix b/instances/heimdall/configuration.nix
index 813aa0f..920b418 100644
--- a/instances/heimdall/configuration.nix
+++ b/instances/heimdall/configuration.nix
@@ -93,6 +93,7 @@ in
       services = {
         # runner for building docker images
         docker-images = {
+          limit = 3;
           authenticationTokenConfigFile = config.age.secrets.heimdall-gitlab-runner-docker-images.path;
 
           dockerImage = "docker:stable";
@@ -102,6 +103,7 @@ in
         };
         # runner for everything else
         default = {
+          limit = 3;
           authenticationTokenConfigFile = config.age.secrets.heimdall-gitlab-runner-default.path;
           dockerImage = "debian:stable";
         };