diff --git a/include/field_specials.h b/include/field_specials.h
index 7bc1e6ad1..b5d1f5c7f 100644
--- a/include/field_specials.h
+++ b/include/field_specials.h
@@ -3,14 +3,6 @@
 
 #include "global.h"
 
-enum HiddenItemAttr
-{
-    HIDDEN_ITEM_ID = 0,
-    HIDDEN_ITEM_FLAG,
-    HIDDEN_ITEM_QUANTITY,
-    HIDDEN_ITEM_UNDERFOOT
-};
-
 u8 GetLeadMonIndex(void);
 s32 CountDigits(s32 number);
 void TV_PrintIntToStringVar(u8 varidx, s32 number);
diff --git a/include/global.fieldmap.h b/include/global.fieldmap.h
index 079b0a4b6..dad5e1d62 100644
--- a/include/global.fieldmap.h
+++ b/include/global.fieldmap.h
@@ -50,6 +50,31 @@ enum
     TILE_TERRAIN_WATERFALL,
 };
 
+// Identifiers for the hidden item data stored in BgEvent's u32 hiddenItem
+enum
+{
+    HIDDEN_ITEM_ITEM,
+    HIDDEN_ITEM_FLAG,
+    HIDDEN_ITEM_QUANTITY,
+    HIDDEN_ITEM_UNDERFOOT
+};
+
+// Masks/shifts to read the data above from the u32 hiddenItem, calculated from size.
+#define HIDDEN_ITEM_ITEM_BITS      16
+#define HIDDEN_ITEM_FLAG_BITS       8
+#define HIDDEN_ITEM_QUANTITY_BITS   7
+#define HIDDEN_ITEM_UNDERFOOT_BITS  1
+
+#define HIDDEN_ITEM_ITEM_SHIFT      0
+#define HIDDEN_ITEM_FLAG_SHIFT      (HIDDEN_ITEM_ITEM_SHIFT + HIDDEN_ITEM_ITEM_BITS)
+#define HIDDEN_ITEM_QUANTITY_SHIFT  (HIDDEN_ITEM_FLAG_SHIFT + HIDDEN_ITEM_FLAG_BITS)
+#define HIDDEN_ITEM_UNDERFOOT_SHIFT (HIDDEN_ITEM_QUANTITY_SHIFT + HIDDEN_ITEM_QUANTITY_BITS)
+
+#define GET_HIDDEN_ITEM_ITEM(raw)     (((raw) >> HIDDEN_ITEM_ITEM_SHIFT)      & ((1 << HIDDEN_ITEM_ITEM_BITS) - 1))
+#define GET_HIDDEN_ITEM_FLAG(raw)     (((raw) >> HIDDEN_ITEM_FLAG_SHIFT)      & ((1 << HIDDEN_ITEM_FLAG_BITS) - 1))
+#define GET_HIDDEN_ITEM_QUANTITY(raw) (((raw) >> HIDDEN_ITEM_QUANTITY_SHIFT)  & ((1 << HIDDEN_ITEM_QUANTITY_BITS) - 1))
+#define GET_HIDDEN_ITEM_UNDERFOOT(raw)(((raw) >> HIDDEN_ITEM_UNDERFOOT_SHIFT) & ((1 << HIDDEN_ITEM_UNDERFOOT_BITS) - 1))
+
 typedef void (*TilesetCB)(void);
 
 struct Tileset
@@ -133,13 +158,7 @@ struct BgEvent
     u8 kind; // The "kind" field determines how to access bgUnion union below.
     union {
         u8 *script;
-        struct {
-            u32 itemId:16;
-            u32 hiddenItemId:8; // flag offset to determine flag lookup
-            u32 quantity:7;
-            u32 isUnderfoot:1;
-        } hiddenItemStr;
-        u32 hiddenItem;
+        u32 hiddenItem; // Contains all the hidden item data. See GET_HIDDEN_ITEM_* defines further up
     } bgUnion;
 };
 
diff --git a/src/field_control_avatar.c b/src/field_control_avatar.c
index 9a7d55edc..1216bec21 100644
--- a/src/field_control_avatar.c
+++ b/src/field_control_avatar.c
@@ -495,11 +495,11 @@ static const u8 *GetInteractedBackgroundEventScript(struct MapPosition *position
     case 5:
     case 6:
     case BG_EVENT_HIDDEN_ITEM:
-        if (GetHiddenItemAttr((u32)bgEvent->bgUnion.script, HIDDEN_ITEM_UNDERFOOT) == TRUE)
+        if (GetHiddenItemAttr(bgEvent->bgUnion.hiddenItem, HIDDEN_ITEM_UNDERFOOT) == TRUE)
             return NULL;
-        gSpecialVar_0x8005 = GetHiddenItemAttr((u32)bgEvent->bgUnion.script, HIDDEN_ITEM_ID);
-        gSpecialVar_0x8004 = GetHiddenItemAttr((u32)bgEvent->bgUnion.script, HIDDEN_ITEM_FLAG);
-        gSpecialVar_0x8006 = GetHiddenItemAttr((u32)bgEvent->bgUnion.script, HIDDEN_ITEM_QUANTITY);
+        gSpecialVar_0x8005 = GetHiddenItemAttr(bgEvent->bgUnion.hiddenItem, HIDDEN_ITEM_ITEM);
+        gSpecialVar_0x8004 = GetHiddenItemAttr(bgEvent->bgUnion.hiddenItem, HIDDEN_ITEM_FLAG);
+        gSpecialVar_0x8006 = GetHiddenItemAttr(bgEvent->bgUnion.hiddenItem, HIDDEN_ITEM_QUANTITY);
         if (FlagGet(gSpecialVar_0x8004) == TRUE)
             return NULL;
         gSpecialVar_Facing = direction;
diff --git a/src/field_specials.c b/src/field_specials.c
index 872c5007d..ba8d70cd3 100644
--- a/src/field_specials.c
+++ b/src/field_specials.c
@@ -1750,15 +1750,15 @@ u16 StickerManGetBragFlags(void)
 
 u16 GetHiddenItemAttr(u32 hiddenItem, u8 attr)
 {
-    if (attr == 0)
-        return hiddenItem & 0xFFFF;
-    else if (attr == 1)
-        return ((hiddenItem >> 16) & 0xFF) + 1000;
-    else if (attr == 2)
-        return (hiddenItem >> 24) & 0x7F;
-    else if (attr == 3)
-        return (hiddenItem >> 31) & 0x01;
-    else
+    if (attr == HIDDEN_ITEM_ITEM)
+        return GET_HIDDEN_ITEM_ITEM(hiddenItem);
+    else if (attr == HIDDEN_ITEM_FLAG)
+        return GET_HIDDEN_ITEM_FLAG(hiddenItem) + FLAG_HIDDEN_ITEMS_START;
+    else if (attr == HIDDEN_ITEM_QUANTITY)
+        return GET_HIDDEN_ITEM_QUANTITY(hiddenItem);
+    else if (attr == HIDDEN_ITEM_UNDERFOOT)
+        return GET_HIDDEN_ITEM_UNDERFOOT(hiddenItem);
+    else // Invalid
         return 1;
 }
 
diff --git a/src/itemfinder.c b/src/itemfinder.c
index 551d0d53b..7819b3944 100644
--- a/src/itemfinder.c
+++ b/src/itemfinder.c
@@ -242,8 +242,8 @@ static void SetUnderfootHiddenItem(u8 taskId, u32 hiddenItem)
 {
     s16 *data = gTasks[taskId].data;
     gSpecialVar_0x8004 = GetHiddenItemAttr(hiddenItem, HIDDEN_ITEM_FLAG);
-    gSpecialVar_0x8005 = GetHiddenItemAttr(hiddenItem, HIDDEN_ITEM_ID);
-    gSpecialVar_0x8006 = 1;
+    gSpecialVar_0x8005 = GetHiddenItemAttr(hiddenItem, HIDDEN_ITEM_ITEM);
+    gSpecialVar_0x8006 = 1; // Quantity. The 'HIDDEN_ITEM_QUANTITY' data is ignored for underfoot items
     TV_PrintIntToStringVar(0, gSpecialVar_0x8005);
     tHiddenItemFound = TRUE;
     tItemX = 0;