diff --git a/lotus/sem_ops/sem_map.py b/lotus/sem_ops/sem_map.py
index 99a5d940..2e903c91 100644
--- a/lotus/sem_ops/sem_map.py
+++ b/lotus/sem_ops/sem_map.py
@@ -126,7 +126,7 @@ def __call__(
             strategy=strategy,
         )
 
-        new_df = self._obj
+        new_df = self._obj.copy()
         new_df[suffix] = outputs
         if return_explanations:
             new_df["explanation" + suffix] = explanations