diff --git a/packages/core/src/Extension.ts b/packages/core/src/Extension.ts
index 74d7820a48a..7b06b95f085 100644
--- a/packages/core/src/Extension.ts
+++ b/packages/core/src/Extension.ts
@@ -357,7 +357,7 @@ export class Extension<Options = any, Storage = any> {
   extend<ExtendedOptions = Options, ExtendedStorage = Storage>(
     extendedConfig: Partial<ExtensionConfig<ExtendedOptions, ExtendedStorage>> = {},
   ) {
-    const extension = new Extension<ExtendedOptions, ExtendedStorage>(extendedConfig)
+    const extension = new Extension<ExtendedOptions, ExtendedStorage>({ ...this.config, ...extendedConfig })
 
     extension.parent = this
 
diff --git a/packages/core/src/Mark.ts b/packages/core/src/Mark.ts
index aa23a478541..7587d659083 100644
--- a/packages/core/src/Mark.ts
+++ b/packages/core/src/Mark.ts
@@ -489,7 +489,7 @@ export class Mark<Options = any, Storage = any> {
   extend<ExtendedOptions = Options, ExtendedStorage = Storage>(
     extendedConfig: Partial<MarkConfig<ExtendedOptions, ExtendedStorage>> = {},
   ) {
-    const extension = new Mark<ExtendedOptions, ExtendedStorage>(extendedConfig)
+    const extension = new Mark<ExtendedOptions, ExtendedStorage>({ ...this.config, ...extendedConfig })
 
     extension.parent = this
 
diff --git a/packages/core/src/Node.ts b/packages/core/src/Node.ts
index 660c1bbd10a..1bdef6be72e 100644
--- a/packages/core/src/Node.ts
+++ b/packages/core/src/Node.ts
@@ -598,7 +598,7 @@ export class Node<Options = any, Storage = any> {
   extend<ExtendedOptions = Options, ExtendedStorage = Storage>(
     extendedConfig: Partial<NodeConfig<ExtendedOptions, ExtendedStorage>> = {},
   ) {
-    const extension = new Node<ExtendedOptions, ExtendedStorage>(extendedConfig)
+    const extension = new Node<ExtendedOptions, ExtendedStorage>({ ...this.config, ...extendedConfig })
 
     extension.parent = this