diff --git a/nixos/modules/services/continuous-integration/gocd-agent/default.nix b/nixos/modules/services/continuous-integration/gocd-agent/default.nix
index 2e9e1c94857..8cae08bf1fa 100644
--- a/nixos/modules/services/continuous-integration/gocd-agent/default.nix
+++ b/nixos/modules/services/continuous-integration/gocd-agent/default.nix
@@ -90,6 +90,7 @@ in {
       };
 
       startupOptions = mkOption {
+        type = types.listOf types.str;
         default = [
           "-Xms${cfg.initialJavaHeapSize}"
           "-Xmx${cfg.maxJavaHeapMemory}"
@@ -105,6 +106,7 @@ in {
 
       extraOptions = mkOption {
         default = [ ];
+        type = types.listOf types.str;
         example = [
           "-X debug"
           "-Xrunjdwp:transport=dt_socket,server=y,suspend=n,address=5006"
diff --git a/nixos/modules/services/continuous-integration/gocd-server/default.nix b/nixos/modules/services/continuous-integration/gocd-server/default.nix
index 4fa41ac49ed..4c829664a0a 100644
--- a/nixos/modules/services/continuous-integration/gocd-server/default.nix
+++ b/nixos/modules/services/continuous-integration/gocd-server/default.nix
@@ -27,6 +27,7 @@ in {
 
       extraGroups = mkOption {
         default = [ ];
+        type = types.listOf types.str;
         example = [ "wheel" "docker" ];
         description = ''
           List of extra groups that the "gocd-server" user should be a part of.
@@ -92,6 +93,7 @@ in {
       };
 
       startupOptions = mkOption {
+        type = types.listOf types.str;
         default = [
           "-Xms${cfg.initialJavaHeapSize}"
           "-Xmx${cfg.maxJavaHeapMemory}"
@@ -113,6 +115,7 @@ in {
 
       extraOptions = mkOption {
         default = [ ];
+        type = types.listOf types.str;
         example = [
           "-X debug"
           "-Xrunjdwp:transport=dt_socket,server=y,suspend=n,address=5005"