diff --git a/PKHeX.WinForms/MainWindow/Main.cs b/PKHeX.WinForms/MainWindow/Main.cs
index 97991faa1..d5b27fecc 100644
--- a/PKHeX.WinForms/MainWindow/Main.cs
+++ b/PKHeX.WinForms/MainWindow/Main.cs
@@ -3531,7 +3531,11 @@ private void clickLegality(object sender, EventArgs e)
             int slot = getSlot(sender);
             PKM pk;
             if (slot >= 0)
+            {
                 pk = SAV.getStoredSlot(getPKXOffset(slot));
+                if (slot < 30 || slot >= 36) // not party
+                    pk.Box = CB_BoxSelect.SelectedIndex; // mark as in a box
+            }
             else if (verifiedPKM())
                 pk = preparePKM();
             else
diff --git a/PKHeX/Legality/Checks.cs b/PKHeX/Legality/Checks.cs
index c797cc566..5562c928e 100644
--- a/PKHeX/Legality/Checks.cs
+++ b/PKHeX/Legality/Checks.cs
@@ -1677,6 +1677,14 @@ private void verifyForm()
                         return;
                     }
                     break;
+
+                // Party Only Forms
+                case 492: // Shaymin
+                case 676: // Furfrou
+                case 720: // Hoopa
+                    if (pkm.AltForm != 0 && pkm.Box > -1) // has form but stored in box
+                        AddLine(Severity.Invalid, "Form cannot exist outside of Party.", CheckIdentifier.Form);
+                    break;
             }
 
             if (pkm.Format >= 7 && pkm.GenNumber < 7 && pkm.AltForm != 0)