diff --git a/scripts/pack-act-assets.ts b/scripts/pack-act-assets.ts
index 6b10bf1..161d52d 100644
--- a/scripts/pack-act-assets.ts
+++ b/scripts/pack-act-assets.ts
@@ -64,6 +64,8 @@ const PAGE_SIZE = 2048
 const HOT_RADIUS_CELLS = 8
 /** Where object art lives. */
 const OBJECT_PREFIX = 'data\\global\\objects\\'
+/** Where monster and town-NPC art lives. */
+const MONSTER_PREFIX = 'data\\global\\monsters\\'
 /**
  * Mode directories tried in order when picking an object's art.
  *
@@ -347,9 +349,12 @@ const objectMembers = new Map<string, Map<string, string[]>>()
 const monsterMembers = new Map<string, Map<string, string[]>>()
 for (const name of allNames) {
   const isObj = name.toLowerCase().startsWith(OBJECT_PREFIX.toLowerCase())
-  const isMon = name.toLowerCase().startsWith('data\\global\\monsters\\')
+  const isMon = name.toLowerCase().startsWith(MONSTER_PREFIX.toLowerCase())
   if (!isObj && !isMon) continue
-  const prefixLen = isObj ? OBJECT_PREFIX.length : 22 // 'data\\global\\monsters\\'.length
+  // Derive the length; a hand-counted magic number here was off by one (22 vs
+  // the real 21), which sliced the first letter off every monster token and
+  // silently broke all NPC art lookups.
+  const prefixLen = isObj ? OBJECT_PREFIX.length : MONSTER_PREFIX.length
   const rest = name.slice(prefixLen).split('\\')
   if (rest.length < 3) continue
   const token = (rest[0] ?? '').toUpperCase()