diff --git a/packages/netlify-cms-core/index.d.ts b/packages/netlify-cms-core/index.d.ts
index 860bcd8f..070d12ac 100644
--- a/packages/netlify-cms-core/index.d.ts
+++ b/packages/netlify-cms-core/index.d.ts
@@ -347,6 +347,7 @@ declare module 'netlify-cms-core' {
     name: CmsBackendType;
     auth_scope?: CmsAuthScope;
     open_authoring?: boolean;
+    always_fork?: boolean;
     repo?: string;
     branch?: string;
     api_root?: string;