diff --git a/src/documents/serialisers.py b/src/documents/serialisers.py
index c063a72fa..02c3866c6 100644
--- a/src/documents/serialisers.py
+++ b/src/documents/serialisers.py
@@ -2098,6 +2098,8 @@ class BulkEditSerializer(
         if not isinstance(parameters["pages"], str):
             raise serializers.ValidationError("invalid pages specified")
         page_count = Document.objects.get(id=document_id).page_count
+        if not page_count:
+            raise serializers.ValidationError("document page count is unknown")
         pages = []
         for group in parameters["pages"].split(","):
             start, is_range, end = group.partition("-")
@@ -2107,7 +2109,7 @@ class BulkEditSerializer(
             except ValueError as e:
                 raise serializers.ValidationError("invalid pages specified") from e
             # Bound the range before building it, a huge one would exhaust memory
-            if not 1 <= first <= last or (page_count and last > page_count):
+            if not 1 <= first <= last <= page_count:
                 raise serializers.ValidationError("invalid pages specified")
             pages.append(list(range(first, last + 1)))
         parameters["pages"] = pages
diff --git a/src/documents/tests/test_api_bulk_edit.py b/src/documents/tests/test_api_bulk_edit.py
index 275e3aa27..bb43dd8cb 100644
--- a/src/documents/tests/test_api_bulk_edit.py
+++ b/src/documents/tests/test_api_bulk_edit.py
@@ -1784,6 +1784,36 @@ class TestBulkEditAPI(DirectoriesMixin, APITestCase):
                 self.assertIn(b"invalid pages specified", response.content)
         m.assert_not_called()
 
+    @mock.patch("documents.serialisers.bulk_edit.split")
+    def test_bulk_edit_split_rejects_unknown_page_count(self, m) -> None:
+        """
+        GIVEN:
+            - A legacy split bulk edit of a document without a page count
+        WHEN:
+            - API to bulk edit is called
+        THEN:
+            - API returns HTTP 400
+            - split is not called
+        """
+        self.setup_mock(m, "split")
+
+        for pages in ("1", "1-5000000"):
+            with self.subTest(pages=pages):
+                response = self.client.post(
+                    "/api/documents/bulk_edit/",
+                    json.dumps(
+                        {
+                            "documents": [self.doc1.id],
+                            "method": "split",
+                            "parameters": {"pages": pages},
+                        },
+                    ),
+                    content_type="application/json",
+                )
+                self.assertEqual(response.status_code, status.HTTP_400_BAD_REQUEST)
+                self.assertIn(b"document page count is unknown", response.content)
+        m.assert_not_called()
+
     @mock.patch("documents.serialisers.bulk_edit.split")
     def test_bulk_edit_split_parses_pages(self, m) -> None:
         """