diff --git a/data/items_vanilla.json b/data/items_vanilla.json
index 338a0b0..0af74d9 100644
--- a/data/items_vanilla.json
+++ b/data/items_vanilla.json
@@ -5910,7 +5910,7 @@
     "Description": "I蓄电器（满）",
     "IconPath": "Icons/ItemRecipe/accumulator-full",
     "IconTag": "mxdq",
-    "GridIndex": 2114,
+    "GridIndex": 2115,
     "StackSize": 50,
     "Type": 5,
     "PreTechOverride": 1511,
@@ -9050,4 +9050,4 @@
     "EnemyDropMask": 0,
     "EnemyDropMaskRatio": 0.0
   }
-]
\ No newline at end of file
+]
diff --git a/tests/test_item_grid.py b/tests/test_item_grid.py
new file mode 100644
index 0000000..a6c532f
--- /dev/null
+++ b/tests/test_item_grid.py
@@ -0,0 +1,47 @@
+import json
+from pathlib import Path
+import unittest
+
+
+ROOT = Path(__file__).resolve().parents[1]
+ITEM_FILES = [
+    ROOT / "data" / "items_vanilla.json",
+    ROOT / "data" / "items_mod.json",
+]
+MAX_PAGE = 5
+MAX_ROW = 7
+MAX_COLUMN = 17
+
+
+class ItemGridTest(unittest.TestCase):
+    def test_non_zero_item_grid_indices_are_unique_and_in_picker_bounds(self):
+        seen = {}
+        for path in ITEM_FILES:
+            with path.open(encoding="utf-8-sig") as handle:
+                for item in json.load(handle):
+                    grid_index = item["GridIndex"]
+                    if grid_index == 0:
+                        continue
+
+                    item_id = item["ID"]
+                    page = grid_index // 1000
+                    row = (grid_index - page * 1000) // 100
+                    column = grid_index % 100
+
+                    self.assertGreaterEqual(page, 1, f"{item_id} has invalid page in {grid_index}")
+                    self.assertLessEqual(page, MAX_PAGE, f"{item_id} has invalid page in {grid_index}")
+                    self.assertGreaterEqual(row, 1, f"{item_id} has invalid row in {grid_index}")
+                    self.assertLessEqual(row, MAX_ROW, f"{item_id} has invalid row in {grid_index}")
+                    self.assertGreaterEqual(column, 1, f"{item_id} has invalid column in {grid_index}")
+                    self.assertLessEqual(column, MAX_COLUMN, f"{item_id} has invalid column in {grid_index}")
+
+                    self.assertNotIn(
+                        grid_index,
+                        seen,
+                        f"{item_id} and {seen.get(grid_index)} share item GridIndex {grid_index}",
+                    )
+                    seen[grid_index] = item_id
+
+
+if __name__ == "__main__":
+    unittest.main()