diff --git a/src/doomdata.h b/src/doomdata.h
index cfebe196d6..58bfea68af 100644
--- a/src/doomdata.h
+++ b/src/doomdata.h
@@ -372,7 +372,7 @@ struct FMapThing
 	uint32_t		RenderStyle;
 	int			FloatbobPhase;
 	int			friendlyseeblocks;
-	FString arg0str;
+	FNameNoInit arg0str;
 };
 
 
diff --git a/src/p_mobj.cpp b/src/p_mobj.cpp
index 0f77f534d7..79f549dd38 100644
--- a/src/p_mobj.cpp
+++ b/src/p_mobj.cpp
@@ -6098,7 +6098,7 @@ AActor *P_SpawnMapThing (FMapThing *mthing, int position)
 	if (i->IsDescendantOf(RUNTIME_CLASS(ADynamicLight)))
 	{
 		auto light = static_cast<ADynamicLight*>(mobj);
-		if (mthing->arg0str.IsNotEmpty())
+		if (mthing->arg0str != NAME_None)
 		{
 			PalEntry color = V_GetColor(nullptr, mthing->arg0str);
 		}