diff --git a/OpenRA.Mods.Common/UtilityCommands/CheckYaml.cs b/OpenRA.Mods.Common/UtilityCommands/CheckYaml.cs
index 9d6f9a2700..2a96940697 100644
--- a/OpenRA.Mods.Common/UtilityCommands/CheckYaml.cs
+++ b/OpenRA.Mods.Common/UtilityCommands/CheckYaml.cs
@@ -127,7 +127,7 @@ namespace OpenRA.Mods.Common.UtilityCommands
 			{
 				try
 				{
-					modData.RulesetCache.Load(modData.DefaultFileSystem, map);
+					modData.RulesetCache.Load(map ?? modData.DefaultFileSystem, map);
 					var customRulesPass = (ILintRulesPass)modData.ObjectCreator.CreateBasic(customRulesPassType);
 					customRulesPass.Run(EmitError, EmitWarning, rules);
 				}