diff --git a/src/osekit/public/project.py b/src/osekit/public/project.py
index dddabaad..23288dc2 100644
--- a/src/osekit/public/project.py
+++ b/src/osekit/public/project.py
@@ -744,6 +744,10 @@ def delete_transform_with_outputs(self, transform_name: str) -> None:
             Name of the transform whose output to delete.
 
         """
+        if transform_name not in self.transforms:
+            message = f"Transform '{transform_name}' not found."
+            raise ValueError(message)
+
         for dataset_to_delete in self.get_output_by_transform_name(
             transform_name,
         ):
diff --git a/tests/test_public_api.py b/tests/test_public_api.py
index 24be008f..613a8ea6 100644
--- a/tests/test_public_api.py
+++ b/tests/test_public_api.py
@@ -1397,6 +1397,10 @@ def test_delete_output(
         assert all(ds.name in proj.outputs.keys() for ds in datasets_to_keep)
         assert not any(ds.name in proj.outputs.keys() for ds in datasets_to_delete)
 
+    # Trying to delete an unexisting transform should raise:
+    with pytest.raises(ValueError, match="'FrankieCosmos'"):
+        project.delete_transform_with_outputs("FrankieCosmos")
+
 
 def test_existing_output_warning(
     tmp_path: pytest.fixture,