diff --git a/PKHeX/MainWindow/Main.cs b/PKHeX/MainWindow/Main.cs
index a0b108548..bbac3d325 100644
--- a/PKHeX/MainWindow/Main.cs
+++ b/PKHeX/MainWindow/Main.cs
@@ -4204,7 +4204,7 @@ private void pbBoxSlot_MouseMove(object sender, MouseEventArgs e)
                         getQuickFiller(pb, SAV.getStoredSlot(DragInfo.slotSourceOffset));
                     pb.BackgroundImage = null;
                     
-                    if (DragInfo.SameBox)
+                    if (DragInfo.SameBox && DragInfo.DestinationValid)
                         SlotPictureBoxes[DragInfo.slotDestinationSlotNumber].Image = img;
 
                     if (result == DragDropEffects.Copy) // viewed in tabs, apply 'view' highlight
@@ -4242,7 +4242,6 @@ private void pbBoxSlot_DragDrop(object sender, DragEventArgs e)
             if (Directory.Exists(files[0])) { loadBoxesFromDB(files[0]); return; }
             if (DragInfo.SameSlot)
                 return;
-            if (DragInfo.SameBox)
             if (SAV.getIsSlotLocked(DragInfo.slotDestinationBoxNumber, DragInfo.slotDestinationSlotNumber))
             {
                 DragInfo.slotDestinationSlotNumber = -1; // Invalidate
@@ -4368,8 +4367,8 @@ public static class DragInfo
 
             public static bool SameBox => slotSourceBoxNumber > -1 && slotSourceBoxNumber == slotDestinationBoxNumber;
             public static bool SameSlot => slotSourceSlotNumber == slotDestinationSlotNumber && slotSourceBoxNumber == slotDestinationBoxNumber;
-            public static bool SourceValid => slotSourceBoxNumber > -1 || SourceParty;
-            public static bool DestinationValid => slotDestinationBoxNumber > -1 || DestinationParty;
+            public static bool SourceValid => slotSourceSlotNumber > -1 && (slotSourceBoxNumber > -1 || SourceParty);
+            public static bool DestinationValid => slotDestinationSlotNumber > -1 && (slotDestinationBoxNumber > -1 || DestinationParty);
             public static bool SourceParty => 30 <= slotSourceSlotNumber && slotSourceSlotNumber < 36;
             public static bool DestinationParty => 30 <= slotDestinationSlotNumber && slotDestinationSlotNumber < 36;
 
diff --git a/PKHeX/Subforms/Save Editors/SAV_BoxViewer.cs b/PKHeX/Subforms/Save Editors/SAV_BoxViewer.cs
index 43b0d292c..55370fcbe 100644
--- a/PKHeX/Subforms/Save Editors/SAV_BoxViewer.cs	
+++ b/PKHeX/Subforms/Save Editors/SAV_BoxViewer.cs	
@@ -213,7 +213,7 @@ private void pbBoxSlot_MouseMove(object sender, MouseEventArgs e)
                         getQuickFiller(pb, SAV.getStoredSlot(DragInfo.slotSourceOffset));
                     pb.BackgroundImage = null;
 
-                    if (DragInfo.SameBox)
+                    if (DragInfo.SameBox && DragInfo.DestinationValid)
                         SlotPictureBoxes[DragInfo.slotDestinationSlotNumber].Image = img;
                 }
                 catch (Exception x)