diff --git a/safe/sample.py b/safe/sample.py
index 822b9f1..b04796a 100644
--- a/safe/sample.py
+++ b/safe/sample.py
@@ -92,7 +92,7 @@ def load_default(
 
     def linker_generation(
         self,
-        *groups: List[Union[str, dm.Mol]],
+        *groups: Union[str, dm.Mol],
         n_samples_per_trial: int = 10,
         n_trials: Optional[int] = 1,
         sanitize: bool = False,