diff --git a/OpenRA.Game/Traits/World/UnitInfluence.cs b/OpenRA.Game/Traits/World/UnitInfluence.cs
index afaba57b49..fc99253521 100644
--- a/OpenRA.Game/Traits/World/UnitInfluence.cs
+++ b/OpenRA.Game/Traits/World/UnitInfluence.cs
@@ -91,9 +91,10 @@ namespace OpenRA.Traits
 						throw new InvalidOperationException( "UIM: Sanity check failed B" );
 		}
 
+		Actor[] noActors = { };
 		public IEnumerable<Actor> GetUnitsAt( int2 a )
 		{
-			if (!map.IsInMap(a)) return null;
+			if (!map.IsInMap(a)) return noActors;
 			return influence[ a.X, a.Y ];
 		}