diff --git a/python/python/ci_benchmarks/benchmarks/test_merge_insert.py b/python/python/ci_benchmarks/benchmarks/test_merge_insert.py
index b1d0170db24..f2e6ad2fc03 100644
--- a/python/python/ci_benchmarks/benchmarks/test_merge_insert.py
+++ b/python/python/ci_benchmarks/benchmarks/test_merge_insert.py
@@ -95,12 +95,13 @@ def reset(self, cold: bool = False) -> lance.LanceDataset:
 def _open_target(name: str) -> Iterable[Target]:
     uri = get_dataset_uri(name)
     dataset = lance.dataset(uri)
-    base_version = dataset.tags.get_version(BASE_TAG)
-    if base_version is None:
+    tags = dataset.tags.list()
+    if BASE_TAG not in tags:
         pytest.skip(
             f"Dataset {name} has no {BASE_TAG} tag; "
             "run python/ci_benchmarks/datagen/gen_all.py"
         )
+    base_version = tags[BASE_TAG]["version"]
 
     yield Target(uri=uri, dataset=dataset, base_version=base_version)
 
diff --git a/python/python/ci_benchmarks/datagen/merge_insert.py b/python/python/ci_benchmarks/datagen/merge_insert.py
index ebda5730aa2..33f165d8772 100644
--- a/python/python/ci_benchmarks/datagen/merge_insert.py
+++ b/python/python/ci_benchmarks/datagen/merge_insert.py
@@ -257,14 +257,18 @@ def _already_generated(uri: str, expected_rows: int) -> bool:
 
     A previous benchmark run may have left extra versions behind, so the row
     count is checked at the tagged version rather than at the latest one.
+
+    Incomplete generations (dataset written, tag never created) and missing
+    tags both return False so the caller can overwrite and retag.
     """
     try:
         ds = lance.dataset(uri)
     except ValueError:
         return False
-    base_version = ds.tags.get_version(BASE_TAG)
-    if base_version is None:
+    tags = ds.tags.list()
+    if BASE_TAG not in tags:
         return False
+    base_version = tags[BASE_TAG]["version"]
     return ds.checkout_version(base_version).count_rows() == expected_rows
 
 
diff --git a/python/python/lance/dataset.py b/python/python/lance/dataset.py
index 3cdd44ea35e..1da97869668 100644
--- a/python/python/lance/dataset.py
+++ b/python/python/lance/dataset.py
@@ -7240,7 +7240,7 @@ def list(self) -> dict[str, Tag]:
         """
         return self._ds.tags()
 
-    def get_version(self, tag: str) -> Optional[int]:
+    def get_version(self, tag: str) -> int:
         """
         Get the version of a specific tag by name.
 
@@ -7251,8 +7251,13 @@ def get_version(self, tag: str) -> Optional[int]:
 
         Returns
         -------
-        int or None
-            The version number of the tag if it exists, otherwise None.
+        int
+            The version number of the tag.
+
+        Raises
+        ------
+        ValueError
+            If the tag does not exist. Use :meth:`list` to check for presence.
         """
         return self._ds.get_version(tag)