diff --git a/.eslintrc.json b/.eslintrc.json
index 012e888..36c3632 100644
--- a/.eslintrc.json
+++ b/.eslintrc.json
@@ -32,31 +32,7 @@
     ],
     "@typescript-eslint/await-thenable": "error",
     "@typescript-eslint/ban-ts-comment": "warn",
-    "@typescript-eslint/ban-types": [
-      "warn",
-      {
-        "types": {
-          "Object": {
-            "message": "Avoid using the `Object` type. Did you mean `object`?"
-          },
-          "Function": {
-            "message": "Avoid using the `Function` type. Prefer a specific function type, like `() => void`."
-          },
-          "Boolean": {
-            "message": "Avoid using the `Boolean` type. Did you mean `boolean`?"
-          },
-          "Number": {
-            "message": "Avoid using the `Number` type. Did you mean `number`?"
-          },
-          "String": {
-            "message": "Avoid using the `String` type. Did you mean `string`?"
-          },
-          "Symbol": {
-            "message": "Avoid using the `Symbol` type.  Did you mean `symbol`?"
-          }
-        }
-      }
-    ],
+    "@typescript-eslint/ban-types": "off",
     "@typescript-eslint/consistent-type-assertions": "error",
     "@typescript-eslint/dot-notation": "error",
     "@typescript-eslint/explicit-module-boundary-types": "warn",
diff --git a/bootstrap.ts b/bootstrap.ts
index 593ae06..e60a3e9 100644
--- a/bootstrap.ts
+++ b/bootstrap.ts
@@ -130,7 +130,7 @@ export async function startup({ id, version, resourceURI, rootURI = resourceURI.
   }
 }
 
-export function shutdown() {
+export function shutdown(): void {
   log('Shutting down')
 
   if (typeof chromeHandle !== 'undefined') {
@@ -149,7 +149,7 @@ export function shutdown() {
   }
 }
 
-export function uninstall() {
+export function uninstall(): void {
   // `Zotero` object isn't available in `uninstall()` in Zotero 6, so log manually
   if (typeof Zotero == 'undefined') {
     dump('EdTechHub: Uninstalled\n\n')
diff --git a/lib.ts b/lib.ts
index 28cf057..42e2044 100644
--- a/lib.ts
+++ b/lib.ts
@@ -20,19 +20,13 @@ Services.wm.addListener({
 var EdTechHub: EdTechHubMain // eslint-disable-line no-var
 
 import { DebugLog as DebugLogSender } from 'zotero-plugin/debug-log'
+import { patch as $patch$, unpatch as $unpatch$ } from './monkey-patch'
 
 Components.utils.import('resource://gre/modules/osfile.jsm')
 declare const OS: any
 
 import sanitize_filename = require('sanitize-filename')
 
-const marker = 'EdTechHubMonkeyPatched'
-function $patch$(object, method, patcher) {
-  if (object[method][marker]) return
-  object[method] = patcher(object[method])
-  object[method][marker] = true
-}
-
 function flash(title, body = null, timeout = 8) { // eslint-disable-line @typescript-eslint/no-magic-numbers
   try {
     const pw = new Zotero.ProgressWindow()
@@ -149,6 +143,8 @@ function debug(msg, err = null) {
 }
 
 function zotero_itemmenu_popupshowing() {
+  if (!Zotero.EdTechHub) return
+
   const selected = Zotero.getActiveZoteroPane().getSelectedItems()
 
   const doc = Zotero.getMainWindow().document
@@ -240,6 +236,7 @@ class EdTechHubMain {
       XUL: 'http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul',
       HTML: 'http://www.w3.org/1999/xhtml',
     }
+    // eslint-disable-next-line prefer-arrow/prefer-arrow-functions
     function create(name: string, attrs: Record<string, number | string | Function | HTMLElement[]> = {}): HTMLElement {
       const children: HTMLElement[] = (attrs.$ as unknown as HTMLElement[]) || []
       delete attrs.$
@@ -340,6 +337,19 @@ class EdTechHubMain {
       extra: Zotero.ItemFields.getID('extra'),
     }
 
+    $patch$(Zotero.Items, '_mergePDFAttachments', _original => async function(item, otherItems) {
+      Zotero.DB.requireTransaction()
+      for (const otherItem of otherItems) {
+        for (const otherAttachment of await this.getAsync(otherItem.getAttachments(true))) {
+          if (otherAttachment.isPDFAttachment()) {
+            otherAttachment.parentItemID = item.id
+            await otherAttachment.save()
+          }
+        }
+      }
+      return new Map
+    })
+
     $patch$(Zotero.Items, 'merge', original => async function(item, otherItems) {
       let alsoKnownAs: AlsoKnownAs = null
       let history: string = null
@@ -433,6 +443,7 @@ class EdTechHubMain {
     const win = Zotero.getMainWindow()
     const doc = win.document
 
+    $unpatch$()
     doc.getElementById('zotero-itemmenu').removeEventListener('popupshowing', zotero_itemmenu_popupshowing, false)
     for (const elt of Array.from(doc.getElementsByClassName('edtechhub') as HTMLElement[])) {
       elt.remove()