diff --git a/OpenRA.Mods.Common/AI/BaseBuilder.cs b/OpenRA.Mods.Common/AI/BaseBuilder.cs
index 2263d20f97..46a102c75d 100644
--- a/OpenRA.Mods.Common/AI/BaseBuilder.cs
+++ b/OpenRA.Mods.Common/AI/BaseBuilder.cs
@@ -187,7 +187,7 @@ namespace OpenRA.Mods.Common.AI
 		{
 			HashSet<string> actors;
 			if (!ai.Info.BuildingCommonNames.TryGetValue(commonName, out actors))
-				throw new InvalidOperationException("Can't find {0} in the HackyAI BuildingCommonNames definition.".F(commonName));
+				return null;
 
 			var available = buildables.Where(actor =>
 			{
diff --git a/OpenRA.Mods.Common/AI/HackyAI.cs b/OpenRA.Mods.Common/AI/HackyAI.cs
index a3c9e7148a..ca15330896 100644
--- a/OpenRA.Mods.Common/AI/HackyAI.cs
+++ b/OpenRA.Mods.Common/AI/HackyAI.cs
@@ -126,10 +126,11 @@ namespace OpenRA.Mods.Common.AI
 		[Desc("What buildings to the AI should build.", "What % of the total base must be this type of building.")]
 		public readonly Dictionary<string, float> BuildingFractions = null;
 
-		[Desc("Tells the AI what unit types fall under the same common name.")]
+		[Desc("Tells the AI what unit types fall under the same common name. Only supported entry is Mcv.")]
 		public readonly Dictionary<string, HashSet<string>> UnitsCommonNames = null;
 
-		[Desc("Tells the AI what building types fall under the same common name.")]
+		[Desc("Tells the AI what building types fall under the same common name.",
+			"Possible keys are ConstructionYard, Power, Refinery, Silo , Barracks, Production, VehiclesFactory, NavalProduction.")]
 		public readonly Dictionary<string, HashSet<string>> BuildingCommonNames = null;
 
 		[Desc("What buildings should the AI have a maximum limit to build.")]