diff --git a/types/react-bootstrap/lib/FormGroup.d.ts b/types/react-bootstrap/lib/FormGroup.d.ts
index aef2d19f1d..6b7207c215 100644
--- a/types/react-bootstrap/lib/FormGroup.d.ts
+++ b/types/react-bootstrap/lib/FormGroup.d.ts
@@ -6,7 +6,7 @@ declare namespace FormGroup {
         bsClass?: string;
         bsSize?: Sizes;
         controlId?: string;
-        validationState?: "success" | "warning" | "error";
+        validationState?: "success" | "warning" | "error" | null;
     }
 }
 declare class FormGroup extends React.Component<FormGroup.FormGroupProps> { }