diff --git a/antarest/study/common/studystorage.py b/antarest/study/common/studystorage.py
index eb3f561448..59d6311dbf 100644
--- a/antarest/study/common/studystorage.py
+++ b/antarest/study/common/studystorage.py
@@ -253,30 +253,3 @@ def archive_study_output(self, study: T, output_id: str) -> bool:
     @abstractmethod
     def unarchive_study_output(self, study: T, output_id: str, keep_src_zip: bool) -> bool:
         raise NotImplementedError()
-
-    def unarchive(self, study: T) -> None:
-        """
-        Unarchived a study
-        Args:
-            study: StudyFactory
-        """
-        raise NotImplementedError()
-
-    def export_study_flat(
-        self,
-        path_study: Path,
-        dst_path: Path,
-        outputs: bool = True,
-        output_src_path: Optional[Path] = None,
-        output_list_filter: Optional[List[str]] = None,
-    ) -> None:
-        """
-        Export study to destination
-        Args:
-            path_study: source path.
-            dst_path: destination path.
-            outputs: list of outputs to keep.
-            output_src_path: list output path
-            output_list_filter:list of outputs to keep
-        """
-        raise NotImplementedError()
diff --git a/antarest/study/service.py b/antarest/study/service.py
index f5c5b5a164..c2e7d5da8b 100644
--- a/antarest/study/service.py
+++ b/antarest/study/service.py
@@ -922,6 +922,7 @@ def export_task(notifier: TaskUpdateNotifier) -> TaskResult:
                 target_study = self.get_study(uuid)
                 storage = self.storage_service.get_storage(target_study)
                 if isinstance(target_study, RawStudy):
+                    storage = cast(RawStudyService, storage)
                     if target_study.archived:
                         storage.unarchive(target_study)
                     try:
@@ -1035,6 +1036,7 @@ def export_study_flat(
         path_study = Path(study.path)
         storage = self.storage_service.get_storage(study)
         if isinstance(study, RawStudy):
+            storage = cast(RawStudyService, storage)
             if study.archived:
                 storage.unarchive(study)
             try:
@@ -1048,15 +1050,17 @@ def export_study_flat(
             finally:
                 if study.archived:
                     shutil.rmtree(study.path)
-        snapshot_path = path_study / "snapshot"
-        output_src_path = path_study / "output"
-        return storage.export_study_flat(
-            path_study=snapshot_path,
-            dst_path=dest,
-            outputs=len(output_list or []) > 0,
-            output_list_filter=output_list,
-            output_src_path=output_src_path,
-        )
+        else:
+            snapshot_path = path_study / "snapshot"
+            output_src_path = path_study / "output"
+            storage = cast(VariantStudyService, storage)
+            return storage.export_study_flat(
+                path_study=snapshot_path,
+                dst_path=dest,
+                outputs=len(output_list or []) > 0,
+                output_list_filter=output_list,
+                output_src_path=output_src_path,
+            )
 
     def delete_study(self, uuid: str, children: bool, params: RequestParameters) -> None:
         """