diff --git a/src/decallib.cpp b/src/decallib.cpp
index 08b4dfda20..14b824a7b7 100644
--- a/src/decallib.cpp
+++ b/src/decallib.cpp
@@ -603,16 +603,17 @@ void FDecalLib::ParseGenerator (FScanner &sc)
 {
 	const PClass *type;
 	FDecalBase *decal;
-	AActor *actor;
+	bool optional = false;
 
 	// Get name of generator (actor)
 	sc.MustGetString ();
+	optional = sc.Compare("optional");
+
 	type = PClass::FindClass (sc.String);
 	if (type == NULL || type->ActorInfo == NULL)
 	{
-		sc.ScriptError ("%s is not an actor.", sc.String);
+		if (!optional) sc.ScriptError ("%s is not an actor.", sc.String);
 	}
-	actor = (AActor *)type->Defaults;
 
 	// Get name of generated decal
 	sc.MustGetString ();
@@ -628,11 +629,14 @@ void FDecalLib::ParseGenerator (FScanner &sc)
 			sc.ScriptError ("%s has not been defined.", sc.String);
 		}
 	}
-
-	actor->DecalGenerator = decal;
-	if (decal != NULL)
+	if (type != NULL)
 	{
-		decal->Users.Push (type);
+		AActor *actor = (AActor *)type->Defaults;
+		actor->DecalGenerator = decal;
+		if (decal != NULL)
+		{
+			decal->Users.Push(type);
+		}
 	}
 }