diff --git a/PKHeX.Core/PKM/BK4.cs b/PKHeX.Core/PKM/BK4.cs
index 53dbc46a5..bedbe0006 100644
--- a/PKHeX.Core/PKM/BK4.cs
+++ b/PKHeX.Core/PKM/BK4.cs
@@ -16,9 +16,7 @@ public class BK4 : PKM // Big Endian 4th Generation PKM File
 
         public override byte[] DecryptedBoxData => EncryptedBoxData;
 
-        public override string Extension => "bk4";
-
-        public override bool Valid => ChecksumValid || (Sanity != 0 && Species <= 493); // What does Sanity do?
+        public override bool Valid => ChecksumValid || Sanity == 0 && Species <= 493;
 
         public BK4(byte[] decryptedData = null, string ident = null)
         {
diff --git a/PKHeX.Core/PKM/PKM.cs b/PKHeX.Core/PKM/PKM.cs
index d4f68151a..e4c0e01fd 100644
--- a/PKHeX.Core/PKM/PKM.cs
+++ b/PKHeX.Core/PKM/PKM.cs
@@ -8,7 +8,7 @@ public abstract class PKM
         public static readonly string[] Extensions = PKX.getPKMExtensions();
         public abstract int SIZE_PARTY { get; }
         public abstract int SIZE_STORED { get; }
-        public virtual string Extension => "pk" + Format;
+        public string Extension => GetType().Name.ToLower();
         public abstract PersonalInfo PersonalInfo { get; }
 
         // Internal Attributes set on creation
diff --git a/PKHeX.WinForms/Subforms/SAV_FolderList.cs b/PKHeX.WinForms/Subforms/SAV_FolderList.cs
index ea6c88296..b3b221881 100644
--- a/PKHeX.WinForms/Subforms/SAV_FolderList.cs
+++ b/PKHeX.WinForms/Subforms/SAV_FolderList.cs
@@ -53,7 +53,7 @@ private void addButton(string name, string path)
 
         private static IEnumerable<CustomFolderPath> getUserPaths()
         {
-            const string loc = "savpaths.txt";
+            string loc = Path.Combine(Main.WorkingDirectory, "savpaths.txt");
 
             if (!File.Exists(loc))
                 yield break;