diff --git a/PKHeX.Core/PKM/PKX.cs b/PKHeX.Core/PKM/PKX.cs
index 29f0c03c9..274f6ca12 100644
--- a/PKHeX.Core/PKM/PKX.cs
+++ b/PKHeX.Core/PKM/PKX.cs
@@ -823,6 +823,31 @@ public static string[] GetPKMExtensions(int MaxGeneration = Generation)
             return result.ToArray();
         }
 
+        /// <summary>
+        /// Roughly detects the PKM format from the file's extension.
+        /// </summary>
+        /// <param name="ext">File extension.</param>
+        /// <param name="prefer">Preference if not a valid extension, usually the highest acceptable format.</param>
+        /// <returns>Format hint that the file is.</returns>
+        public static int GetPKMFormatFromExtension(string ext, int prefer)
+        {
+            return ext?.Length > 1
+                ? GetPKMFormatFromExtension(ext[ext.Length - 1], prefer) 
+                : prefer;
+        }
+        /// <summary>
+        /// Roughly detects the PKM format from the file's extension.
+        /// </summary>
+        /// <param name="last">Last character of the file's extensio.n</param>
+        /// <param name="prefer">Preference if not a valid extension, usually the highest acceptable format.</param>
+        /// <returns>Format hint that the file is.</returns>
+        public static int GetPKMFormatFromExtension(char last, int prefer)
+        {
+            if ('1' <= last && last <= '9')
+                return last - '0';
+            return last == 'x' ? 6 : prefer;
+        }
+
         // Extensions
         /// <summary>
         /// Gets the Location Name for the <see cref="PKM"/>
diff --git a/PKHeX.WinForms/Controls/SAV Editor/SlotChangeManager.cs b/PKHeX.WinForms/Controls/SAV Editor/SlotChangeManager.cs
index 8e36c98ce..b6465fbaa 100644
--- a/PKHeX.WinForms/Controls/SAV Editor/SlotChangeManager.cs	
+++ b/PKHeX.WinForms/Controls/SAV Editor/SlotChangeManager.cs	
@@ -3,7 +3,6 @@
 using System.Diagnostics;
 using System.Drawing;
 using System.IO;
-using System.Linq;
 using System.Threading.Tasks;
 using System.Windows.Forms;
 using PKHeX.Core;
@@ -235,8 +234,9 @@ private bool TryLoadFiles(string[] files, DragEventArgs e, bool noEgg)
 
             byte[] data = File.ReadAllBytes(file);
             MysteryGift mg = MysteryGift.GetMysteryGift(data, fi.Extension);
-            PKM temp = mg?.ConvertToPKM(SAV) ?? PKMConverter.GetPKMfromBytes(data,
-                           prefer: fi.Extension.Length > 0 ? (fi.Extension.Last() - '0') & 0xF : SAV.Generation);
+            if (fi.Extension.Length > 0 || !int.TryParse(fi.Extension[fi.Extension.Length - 1].ToString(), out var prefer))
+                prefer = SAV.Generation;
+            PKM temp = mg?.ConvertToPKM(SAV) ?? PKMConverter.GetPKMfromBytes(data, prefer: prefer);
 
             PKM pk = PKMConverter.ConvertToType(temp, SAV.PKMType, out string c);
             if (pk == null)
diff --git a/PKHeX.WinForms/MainWindow/Main.cs b/PKHeX.WinForms/MainWindow/Main.cs
index 0f67dceca..9cf47e792 100644
--- a/PKHeX.WinForms/MainWindow/Main.cs
+++ b/PKHeX.WinForms/MainWindow/Main.cs
@@ -576,7 +576,7 @@ private bool TryLoadMemoryCard(byte[] input, string path)
         }
         private bool TryLoadPKM(byte[] input, string ext)
         {
-            var pk = PKMConverter.GetPKMfromBytes(input, prefer: ext.Length > 0 ? (ext.Last() - '0') & 0xF : C_SAV.SAV.Generation);
+            var pk = PKMConverter.GetPKMfromBytes(input, prefer: PKX.GetPKMFormatFromExtension(ext, C_SAV.SAV.Generation));
             if (pk == null)
                 return false;
             
diff --git a/PKHeX.WinForms/Subforms/PKM Editors/BatchEditor.cs b/PKHeX.WinForms/Subforms/PKM Editors/BatchEditor.cs
index c0e76d1fc..2625710c1 100644
--- a/PKHeX.WinForms/Subforms/PKM Editors/BatchEditor.cs	
+++ b/PKHeX.WinForms/Subforms/PKM Editors/BatchEditor.cs	
@@ -276,7 +276,7 @@ private void ProcessFolder(IReadOnlyList<string> files, IList<StringInstruction>
                     continue;
                 }
 
-                int format = fi.Extension.Length > 0 ? (fi.Extension.Last() - '0') & 0xF : SAV.Generation;
+                int format = PKX.GetPKMFormatFromExtension(fi.Extension, SAV.Generation);
                 byte[] data = File.ReadAllBytes(file);
                 var pkm = PKMConverter.GetPKMfromBytes(data, prefer: format);
                 if (ProcessPKM(pkm, Filters, Instructions))
diff --git a/PKHeX.WinForms/Subforms/SAV_Database.cs b/PKHeX.WinForms/Subforms/SAV_Database.cs
index cfdc5e1be..514dbbcef 100644
--- a/PKHeX.WinForms/Subforms/SAV_Database.cs
+++ b/PKHeX.WinForms/Subforms/SAV_Database.cs
@@ -338,7 +338,9 @@ private void LoadDatabase()
             {
                 FileInfo fi = new FileInfo(file);
                 if (!fi.Extension.Contains(".pk") || !PKX.IsPKM(fi.Length)) return;
-                var pk = PKMConverter.GetPKMfromBytes(File.ReadAllBytes(file), file, prefer: (fi.Extension.Last() - '0') & 0xF);
+                var data = File.ReadAllBytes(file);
+                var prefer = PKX.GetPKMFormatFromExtension(fi.Extension, SAV.Generation);
+                var pk = PKMConverter.GetPKMfromBytes(data, file, prefer);
                 if (pk != null)
                     dbTemp.Add(pk);
             });
diff --git a/Tests/PKHeX.Tests/Legality/LegalityTests.cs b/Tests/PKHeX.Tests/Legality/LegalityTests.cs
index 607ed8618..910e6b5ad 100644
--- a/Tests/PKHeX.Tests/Legality/LegalityTests.cs
+++ b/Tests/PKHeX.Tests/Legality/LegalityTests.cs
@@ -49,7 +49,7 @@ private static void VerifyAll(string folder, string name, bool IsValid)
                 Assert.IsTrue(PKX.IsPKM(fi.Length), $"Invalid file in {fi.Directory.Name} folder.");
 
                 var data = File.ReadAllBytes(file);
-                var format = file[file.Length - 1] - '0';
+                var format = PKX.GetPKMFormatFromExtension(file[file.Length - 1], -1);
                 if (format > 10)
                     format = 6;
                 var pkm = PKMConverter.GetPKMfromBytes(data, prefer: format);