diff --git a/src/core/Game2.lua b/src/core/Game2.lua
index 112859eb..7871cbdd 100644
--- a/src/core/Game2.lua
+++ b/src/core/Game2.lua
@@ -683,7 +683,10 @@ end
 -- .SelectMon / PPRestoreItem_Cancel carry path: nothing spent.
 function Game2:usePartyItem(itemId)
   local ItemEffects = require("src.core.gen2.ItemEffects")
-  local action = ItemEffects.partyAction(itemId)
+  -- without the merged dataset this can only ever see RECORDS, the
+  -- module's own built-ins, so a mod's field item resolves to no action
+  -- at all and never gets past the .Oak refusal below
+  local action = ItemEffects.partyAction(itemId, self.data)
   if not action then return end
   local party = (self.save and self.save.party) or {}
   if #party == 0 then
diff --git a/src/ui/gen2/BattleState.lua b/src/ui/gen2/BattleState.lua
index 2d65eeda..bbbc248c 100644
--- a/src/ui/gen2/BattleState.lua
+++ b/src/ui/gen2/BattleState.lua
@@ -3024,8 +3024,10 @@ function BattleState:useItem(itemId)
     -- Everything else the pack can spend on a party mon runs the same
     -- item_effects.asm routine the field pack runs: the potion line and the
     -- drinks, the status cures and their berries, REVIVE / MAX REVIVE, and
-    -- the ETHER / ELIXER family.
-    local action = ItemEffects.partyAction(itemId)
+    -- the ETHER / ELIXER family.  Without the merged dataset this can only
+    -- ever see RECORDS, the module's own built-ins, the same gap
+    -- Game2:usePartyItem had for the field pack.
+    local action = ItemEffects.partyAction(itemId, self.game and self.game.data)
     if action then
       return self:useOnPartyMon(itemId, action)
     end
diff --git a/tests/gen2_battle_items_test.lua b/tests/gen2_battle_items_test.lua
index dbfc8527..186e4596 100644
--- a/tests/gen2_battle_items_test.lua
+++ b/tests/gen2_battle_items_test.lua
@@ -117,6 +117,27 @@ local DATA = {
       fieldMenu = "ITEMMENU_PARTY", battleMenu = "ITEMMENU_NOUSE" },
     OLD_ROD = { id = "OLD_ROD", pocket = "KEY", name = "OLD ROD",
       fieldMenu = "ITEMMENU_CURRENT", battleMenu = "ITEMMENU_NOUSE" },
+    -- a mod's own battle-pack item: its action lives only in
+    -- gen2ItemEffects below, which ItemEffects.RECORDS (the module's
+    -- built-in table) has never heard of (#8)
+    MOD_ITEM = item("MOD_ITEM"),
+  },
+  gen2ItemEffects = {
+    -- a status cure rather than an HP heal: HP is exposed to the wild
+    -- mon's own reply once the item spends the turn, which would make a
+    -- direct before/after HP check depend on incidental battle math this
+    -- fix has nothing to do with.  Status is not.
+    MOD_ITEM = {
+      action = "status", field = true, needsTarget = true,
+      use = function(ctx)
+        local mon = ctx.mon
+        if mon.status ~= "poison" then
+          return { used = false, text = "It won't have\nany effect." }
+        end
+        mon.status = nil
+        return { used = true, text = "MOD ITEM used!" }
+      end,
+    },
   },
 }
 
@@ -236,6 +257,33 @@ do
   eq(save.inventory.ANTIDOTE, 1, "with the ANTIDOTE untouched")
 end
 
+-- ---- a mod's own battle-pack item (#8) -------------------------------------
+-- BattleState:useItem asked ItemEffects.partyAction for the item's family
+-- with no `data` argument, the same omission Game2:usePartyItem had for the
+-- field pack, so a mod item's action -- present only in the merged
+-- gen2ItemEffects table -- resolved to nil and the pack fell straight to
+-- "That isn't going to help here." instead of opening the party list.
+do
+  local sick = Mon.new(DATA, "CYNDAQUIL", 10, { dvs = perfect })
+  sick.moves = { { id = "TACKLE", pp = 35, maxPp = 35 } }
+  sick.status = "poison"
+  local screen, _, _, save, pushed = newScreen({
+    player = sick, party = { sick }, inventory = { MOD_ITEM = 1 },
+  })
+  check(runToMenu(screen), "reached the menu")
+
+  screen:useItem("MOD_ITEM")
+  eq(screen.phase, "submenu",
+    "a mod's own gen2ItemEffects record opens UseItem_SelectMon")
+  local picker = pushed[#pushed]
+  eq(getmetatable(picker), PartyMenu, "and the pick is the party screen")
+  if picker and picker.onChoose then
+    picker.onChoose(1, sick)
+    eq(sick.status, nil, "the mod item's own use() ran through the real screens")
+    eq(save.inventory.MOD_ITEM, nil, "and the mod item was spent")
+  end
+end
+
 -- ---- IsItemUsedOnConfusedMon: the battle-only arm --------------------------
 do
   local screen, battle, player, save, pushed = newScreen({
diff --git a/tests/gen2_field_items_test.lua b/tests/gen2_field_items_test.lua
index c3f9ab68..63e36568 100644
--- a/tests/gen2_field_items_test.lua
+++ b/tests/gen2_field_items_test.lua
@@ -102,6 +102,24 @@ local DATA = {
     TM01 = { id = "TM01", name = "TM01", pocket = "TM_HM", index = 191,
       fieldMenu = "ITEMMENU_PARTY", battleMenu = "ITEMMENU_NOUSE",
       teaches = "SWIFT" },
+    -- a mod's own field item, whose action lives only in gen2ItemEffects
+    -- below -- ItemEffects.RECORDS (the module's built-in table) has never
+    -- heard of it, so resolving it at all requires the merged dataset (#8)
+    MOD_ITEM = { id = "MOD_ITEM", name = "MOD ITEM", pocket = "ITEM",
+      index = 250, fieldMenu = "ITEMMENU_PARTY", battleMenu = "ITEMMENU_PARTY" },
+  },
+  gen2ItemEffects = {
+    MOD_ITEM = {
+      action = "heal", field = true, needsTarget = true,
+      use = function(ctx)
+        local mon = ctx.mon
+        if mon.hp >= mon.maxHp then
+          return { used = false, text = "It won't have\nany effect." }
+        end
+        mon.hp = math.min(mon.maxHp, mon.hp + 5)
+        return { used = true, text = "MOD ITEM used!" }
+      end,
+    },
   },
   gen2MenuGfx = {},
   gen2Icons = {
@@ -461,6 +479,24 @@ do
   eq(host.save.inventory.HP_UP, nil, "and the HP UP was spent")
 end
 
+do
+  -- #8 regression: Game2:usePartyItem asked ItemEffects.partyAction for the
+  -- item's family with no `data` argument, so it could only ever see
+  -- RECORDS -- the module's own built-ins.  A mod's field item, whose
+  -- action exists only in the merged gen2ItemEffects table, resolved to a
+  -- nil action and fell straight through to the "isn't going to help here"
+  -- refusal instead of opening the party list at all.
+  local mon = fixtureMon(12, { hp = 10 })
+  local host = newHost({ MOD_ITEM = 1 }, { mon })
+  host:useFieldItem("MOD_ITEM")
+  local party = host.stack:top()
+  check(party ~= nil and party.prompt ~= nil,
+    "a mod's own gen2ItemEffects record opens the party list")
+  drive(host, function() return host.stack:top() ~= party end)
+  eq(mon.hp, 15, "the mod item's own use() ran through the real menu")
+  eq(host.save.inventory.MOD_ITEM, nil, "and the mod item was spent")
+end
+
 do
   local mon = fixtureMon(12, { statExp = {
     hp = 25600, attack = 0, defense = 0, speed = 0, special = 0 } })