diff --git a/BookSmart/Program.cs b/BookSmart/Program.cs
index 10ba3a4..f370697 100644
--- a/BookSmart/Program.cs
+++ b/BookSmart/Program.cs
@@ -166,10 +166,9 @@ public static List<string> CreateQuestBookCache(IPatcherState<ISkyrimMod, ISkyri
 
         public static string? GetSkillLabelName(IBookGetter book)
         {
-            // variables for use in this section
-            if (book.Teaches == null) { return null; }
-            IBookSkillGetter skillTeach = (IBookSkillGetter)book.Teaches;
-            if (skillTeach == null || skillTeach.Skill == null) { return null; }
+            if (book.Teaches is not IBookSkillGetter skillTeach) return null;
+            if (skillTeach.Skill == null) return null;
+            if ((int)skillTeach.Skill == -1) return null;
 
             // Label Format: Long
             if (settings.labelFormat == Settings.LabelFormat.Long)