diff --git a/app/routes/datasets/versions.py b/app/routes/datasets/versions.py
index 081ee3ac..5288357b 100644
--- a/app/routes/datasets/versions.py
+++ b/app/routes/datasets/versions.py
@@ -13,7 +13,6 @@
 from copy import deepcopy
 from typing import Any, Dict, List, Optional, Sequence, Tuple, Union, cast
 from urllib.parse import urlparse
-import fiona
 
 from fastapi import (
     APIRouter,
@@ -45,6 +44,7 @@
     CreationOptions,
     CreationOptionsResponse,
     creation_option_factory,
+    TableDrivers
 )
 from ...models.pydantic.extent import Extent, ExtentResponse
 from ...models.pydantic.metadata import (
@@ -242,21 +242,26 @@ async def append_to_version(
     input_data["creation_options"]["source_uri"] = request.source_uri
 
     # If source_driver is "text", this is a datapump request
-    if input_data["creation_options"]["source_driver"] != "text":
+    if input_data["creation_options"]["source_driver"] != TableDrivers.text:
         # Verify that source_driver is not None
         if input_data["creation_options"]["source_driver"] is None:
             raise HTTPException(
                 status_code=400,
                 detail="Source driver must be specified for non-datapump requests."
             )
+        
+        # Verify that source_driver matches the original source_driver
+        if input_data["creation_options"]["source_driver"] != request.source_driver:
+            raise HTTPException(
+                status_code=400,
+                detail="source_driver must match the original source_driver."
+            )
 
-        # Append the new layers to the existing ones
-        if input_data["creation_options"].get("layers") is None: # ERROR: layers is not defined
+        # Use layers from request if provided, otherwise leave empty
+        if request.layers is not None:
             input_data["creation_options"]["layers"] = request.layers
-        elif request.layers is not None:
-            input_data["creation_options"]["layers"] += request.layers
         else:
-            input_data["creation_options"]["layers"] = request.layers
+            input_data["creation_options"]["layers"] = None
             
     background_tasks.add_task(
         append_default_asset, dataset, version, input_data, default_asset.asset_id
@@ -264,7 +269,7 @@ async def append_to_version(
 
     # We now want to append the new uris to the existing ones and update the asset
     update_data = {"creation_options": deepcopy(default_asset.creation_options)}
-    update_data["creation_options"]["source_uri"] += request.source_uri # ERROR: only one source_uri is allowed
+    update_data["creation_options"]["source_uri"] += request.source_uri 
     if input_data["creation_options"].get("layers") is not None:
         if update_data["creation_options"]["layers"] is not None:
             update_data["creation_options"]["layers"] += request.layers
@@ -559,18 +564,6 @@ async def _version_response(
 
     return VersionResponse(data=Version(**data))
 
-#def _verify_layer_exists(source_uri: List[str], layes: List[str]) -> None:
-#    with fiona.open(source_uri[0].replace("s3://", "/vsizip//vsis3/"), "r") as src:
-#        layers = src.layer_names
-#        for layer in layers:
-#            if layer in layers:
-#                return
-#            else:
-#                raise HTTPException(
-#                    status_code=400,
-#                    detail=f"Layer {layer} not found in source file."
-#                )
-
 def _verify_source_file_access(sources: List[str]) -> None:
 
     # TODO: