diff --git a/packages/tiptap-core/src/Editor.ts b/packages/tiptap-core/src/Editor.ts
index 2992c8de..161e420c 100644
--- a/packages/tiptap-core/src/Editor.ts
+++ b/packages/tiptap-core/src/Editor.ts
@@ -11,14 +11,16 @@ import { gapCursor } from 'prosemirror-gapcursor'
 import elementFromString from './utils/elementFromString'
 import injectCSS from './utils/injectCSS'
 import ExtensionManager from './ExtensionManager'
+import Extension from './Extension'
+import Node from './Node'
 
 type EditorContent = string | JSON
 type Command = (next: Function, editor: Editor, ...args: any) => any
 
 interface Options {
-  element?: Node
+  element?: globalThis.Node
   content: EditorContent
-  extensions: [any?]
+  extensions: (Extension | Node)[]
   injectCSS: Boolean
 }
 
diff --git a/packages/tiptap-core/src/Extension.ts b/packages/tiptap-core/src/Extension.ts
index ac57a052..f7e37e0b 100644
--- a/packages/tiptap-core/src/Extension.ts
+++ b/packages/tiptap-core/src/Extension.ts
@@ -18,9 +18,9 @@ export default abstract class Extension {
   
   public type = 'extension'
 
-  protected created() {}
+  public created() {}
 
-  protected bindEditor(editor: Editor): void {
+  public bindEditor(editor: Editor): void {
     this.editor = editor
   }
 
diff --git a/packages/tiptap-core/src/ExtensionManager.ts b/packages/tiptap-core/src/ExtensionManager.ts
index eb10958e..29c541f0 100644
--- a/packages/tiptap-core/src/ExtensionManager.ts
+++ b/packages/tiptap-core/src/ExtensionManager.ts
@@ -1,12 +1,14 @@
 import { keymap } from 'prosemirror-keymap'
 import collect from 'collect.js'
 import { Editor } from './Editor'
+import Extension from './Extension'
+import Node from './Node'
 
 export default class ExtensionManager {
 
-  extensions: [any?]
+  extensions: (Extension | Node)[]
 
-  constructor(extensions: any = [], editor: Editor) {
+  constructor(extensions: (Extension | Node)[], editor: Editor) {
     this.extensions = extensions
     this.extensions.forEach(extension => {
       extension.bindEditor(editor)
@@ -15,7 +17,7 @@ export default class ExtensionManager {
   }
 
   get topNode() {
-    const topNode = this.extensions.find(extension => extension.topNode)
+    const topNode = collect(this.extensions).firstWhere('topNode', true)
 
     if (topNode) {
       return topNode.name