diff --git a/packages/core/src/Extension.ts b/packages/core/src/Extension.ts
index ae5870837..fa649aa34 100644
--- a/packages/core/src/Extension.ts
+++ b/packages/core/src/Extension.ts
@@ -474,9 +474,9 @@ export class Extension<Options = any, Storage = any> {
   }
 
   extend<ExtendedOptions = Options, ExtendedStorage = Storage>(
-    extendedConfig: Partial<ExtensionConfig<Partial<ExtendedOptions>, Partial<ExtendedStorage>>> = {},
+    extendedConfig: Partial<ExtensionConfig<ExtendedOptions, ExtendedStorage>> = {},
   ) {
-    const extension = new Extension<ExtendedOptions, ExtendedStorage>({ ...this.config, ...extendedConfig } as ExtensionConfig)
+    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 3200f705f..ea57edd7f 100644
--- a/packages/core/src/Mark.ts
+++ b/packages/core/src/Mark.ts
@@ -606,9 +606,9 @@ export class Mark<Options = any, Storage = any> {
   }
 
   extend<ExtendedOptions = Options, ExtendedStorage = Storage>(
-    extendedConfig: Partial<MarkConfig<Partial<ExtendedOptions>, Partial<ExtendedStorage>>> = {},
+    extendedConfig: Partial<MarkConfig<ExtendedOptions, ExtendedStorage>> = {},
   ) {
-    const extension = new Mark<ExtendedOptions, ExtendedStorage>(extendedConfig as MarkConfig)
+    const extension = new Mark<ExtendedOptions, ExtendedStorage>(extendedConfig)
 
     extension.parent = this
 
diff --git a/packages/core/src/Node.ts b/packages/core/src/Node.ts
index 05ef81539..567e0eef7 100644
--- a/packages/core/src/Node.ts
+++ b/packages/core/src/Node.ts
@@ -816,9 +816,9 @@ export class Node<Options = any, Storage = any> {
   }
 
   extend<ExtendedOptions = Options, ExtendedStorage = Storage>(
-    extendedConfig: Partial<NodeConfig<Partial<ExtendedOptions>, Partial<ExtendedStorage>>> = {},
+    extendedConfig: Partial<NodeConfig<ExtendedOptions, ExtendedStorage>> = {},
   ) {
-    const extension = new Node<ExtendedOptions, ExtendedStorage>(extendedConfig as NodeConfig)
+    const extension = new Node<ExtendedOptions, ExtendedStorage>(extendedConfig)
 
     extension.parent = this