diff --git a/packages/core/src/utils/generateHtml.ts b/packages/core/src/utils/generateHtml.ts
index b21f8a6d..e1f1b6f4 100644
--- a/packages/core/src/utils/generateHtml.ts
+++ b/packages/core/src/utils/generateHtml.ts
@@ -1,16 +1,23 @@
 import getSchema from './getSchema'
 import { Node as ProseMirrorNode, DOMSerializer } from 'prosemirror-model'
 import { Extensions } from '../types'
+import { Schema } from 'prosemirror-model'
 
-export default function generateHtml(doc: object, extensions: Extensions): string {
-  const schema = getSchema(extensions)
+export default function generateHtml(doc: object, schema: (Extensions | Schema)): string {
+  let useSchema
 
-  let contentNode = ProseMirrorNode.fromJSON(schema, doc)
-  let temporaryDocument = document.implementation.createHTMLDocument()
+  if (Array.isArray(schema)) {
+    useSchema = getSchema(schema as Extensions)
+  } else {
+    useSchema = schema as Schema
+  }
+
+  const contentNode = ProseMirrorNode.fromJSON(useSchema, doc)
+  const temporaryDocument = document.implementation.createHTMLDocument()
   const container = temporaryDocument.createElement('div')
 
   const fragment = DOMSerializer
-    .fromSchema(schema)
+    .fromSchema(useSchema)
     .serializeFragment(contentNode.content)
 
   container.appendChild(fragment)