diff --git a/.gitignore b/.gitignore
index 9b847b2..1366b03 100644
--- a/.gitignore
+++ b/.gitignore
@@ -4,6 +4,7 @@
 *~
 .ve
 .ve2
+.DS_Store
 *.pyc
 __pycache__
 .pytest_cache/
@@ -18,6 +19,7 @@ geckodriver.log
 ghostdriver.log
 cove/lib/org-ids.json
 cove/lib/org-ids.json.lock
+lib360dataquality.egg-info/
 chromedriver/
 src/
 node_modules/
diff --git a/.python-version b/.python-version
new file mode 100644
index 0000000..e4fba21
--- /dev/null
+++ b/.python-version
@@ -0,0 +1 @@
+3.12
diff --git a/cove/cove_360/fixtures/badfile_missing_max_row.xlsx b/cove/cove_360/fixtures/badfile_missing_max_row.xlsx
new file mode 100644
index 0000000..023fcd6
Binary files /dev/null and b/cove/cove_360/fixtures/badfile_missing_max_row.xlsx differ
diff --git a/cove/cove_360/tests/test_browser.py b/cove/cove_360/tests/test_browser.py
index 9b6506e..76ce95c 100644
--- a/cove/cove_360/tests/test_browser.py
+++ b/cove/cove_360/tests/test_browser.py
@@ -161,6 +161,9 @@ def server_url(request, live_server):
         'than is supported by this tool (50000). Worksheets with too many rows: '
         '\'grants\' (50001 rows), \'grants_2\' (50002 rows)'
     ], False),
+    ('badfile_missing_max_row.xlsx', [
+        '',
+    ], True),
     ("dei_extension.xlsx", [
         "do not use the 360Giving Data Standard codelists correctly.",
     ], True),
diff --git a/cove/cove_360/views.py b/cove/cove_360/views.py
index c65a0b8..dfaaacd 100644
--- a/cove/cove_360/views.py
+++ b/cove/cove_360/views.py
@@ -154,11 +154,12 @@ def explore_360(request, pk, template='cove_360/explore.html'):
             excessive_sheets = {}
             try:
                 workbook = openpyxl.reader.excel.load_workbook(file_name, read_only=True)
-                excessive_sheets = {
-                    sheetname: workbook[sheetname].max_row
-                    for sheetname in workbook.sheetnames
-                    if workbook[sheetname].max_row > settings.MAX_XLSX_ROWS
-                }
+                for sheetname in workbook.sheetnames:
+                    ws = workbook[sheetname]
+                    if not ws.max_row:
+                        ws.calculate_dimension(force=True)
+                    if ws.max_row > settings.MAX_XLSX_ROWS:
+                        excessive_sheets[sheetname] = ws.max_row
 
             except (zipfile.BadZipFile, openpyxl.utils.exceptions.InvalidFileException):
                 # Exceptions associated with invalid spreadsheets are passed through for cove to handle.