diff --git a/PKHeX.Core/Saves/SAV7.cs b/PKHeX.Core/Saves/SAV7.cs
index 415445300..82f1381b8 100644
--- a/PKHeX.Core/Saves/SAV7.cs
+++ b/PKHeX.Core/Saves/SAV7.cs
@@ -61,7 +61,7 @@ public SAV7(byte[] data = null)
         public override int Generation => 7;
         protected override int GiftCountMax => 48;
         protected override int GiftFlagMax => 0x100 * 8;
-        protected override int EventFlagMax => 3968;
+        protected override int EventFlagMax => USUM ? 4928 : 3968;
         protected override int EventConstMax => (EventFlag - EventConst) / 2;
         public override int OTLength => 12;
         public override int NickLength => 12;
diff --git a/PKHeX.WinForms/Subforms/Save Editors/SAV_EventFlags.cs b/PKHeX.WinForms/Subforms/Save Editors/SAV_EventFlags.cs
index fa7cdb3b3..c8ac2632d 100644
--- a/PKHeX.WinForms/Subforms/Save Editors/SAV_EventFlags.cs	
+++ b/PKHeX.WinForms/Subforms/Save Editors/SAV_EventFlags.cs	
@@ -438,6 +438,8 @@ private void DiffSaves()
 
             SaveFile s1 = SaveUtil.GetVariantSAV(File.ReadAllBytes(TB_OldSAV.Text));
             SaveFile s2 = SaveUtil.GetVariantSAV(File.ReadAllBytes(TB_NewSAV.Text));
+            if (s1 == null) { WinFormsUtil.Alert("Save 1 file invalid."); return; }
+            if (s2 == null) { WinFormsUtil.Alert("Save 2 file invalid."); return; }
 
             if (s1.GetType() != s2.GetType()) { WinFormsUtil.Alert("Save types are different.", $"S1: {s1.GetType().Name}", $"S2: {s2.GetType().Name}"); return; }
             if (s1.Version != s2.Version) { WinFormsUtil.Alert("Save versions are different.", $"S1: {s1.Version}", $"S2: {s2.Version}"); return; }
@@ -455,9 +457,9 @@ private void DiffSaves()
                 {
                     if (oldBits[i] == newBits[i]) continue;
                     if (newBits[i])
-                        tbIsSet += i.ToString("0000") + ",";
+                        tbIsSet += $"{i:0000},";
                     else
-                        tbUnSet += i.ToString("0000") + ",";
+                        tbUnSet += $"{i:0000},";
                 }
             }
             catch (Exception e)